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码场悟道
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< article >
< h1 > 码场悟道< / h1 >
< h1 id = "模板引擎" > < a href = "#模板引擎" class = "headerlink" title = "模板引擎" > < / a > 模板引擎< / h1 > < p > 严格的模板引擎的定义，输入模板字符串 + 数据，得到渲染过的字符串。实现上，从正则替换到拼 function 字符串到正经的 AST 解析各种各样，但从定义上来说都是差不多的。字符串渲染的性能其实也就在后端比较有意义，毕竟每一次渲染都是在消耗服务器资源，但在前端，用户只有一个，几十毫秒的渲染时间跟请求延迟比起来根本不算瓶颈。倒是前端的后续更新是字符串模板引擎的软肋，因为用渲染出来的字符串整个替换 innerHTML 是一个效率很低的更新方式。所以这样的模板引擎如今在纯前端情境下已经不再是好的选择，意义更多是在于方便前后端共用模板。< / p >
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< h1 id = "古老数据渲染-vm-的方式" > < a href = "#古老数据渲染-vm-的方式" class = "headerlink" title = "古老数据渲染 vm 的方式" > < / a > 古老数据渲染 vm 的方式< / h1 > < p > 这种写法，弊端太多了，玩具车< / p >
< pre class = "line-numbers language-markup" data-language = "markup" > < code class = "language-markup" > < span class = "token doctype" > < span class = "token punctuation" > < !< / span > < span class = "token doctype-tag" > DOCTYPE< / span > < span class = "token name" > html< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > html< / span > < span class = "token attr-name" > lang< / span > < span class = "token attr-value" > < span class = "token punctuation attr-equals" > =< / span > < span class = "token punctuation" > "< / span > en< span class = "token punctuation" > "< / span > < / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > head< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > meta< / span > < span class = "token attr-name" > charset< / span > < span class = "token attr-value" > < span class = "token punctuation attr-equals" > =< / span > < span class = "token punctuation" > "< / span > UTF-8< span class = "token punctuation" > "< / span > < / span > < span class = "token punctuation" > />< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > meta< / span > < span class = "token attr-name" > http-equiv< / span > < span class = "token attr-value" > < span class = "token punctuation attr-equals" > =< / span > < span class = "token punctuation" > "< / span > X-UA-Compatible< span class = "token punctuation" > "< / span > < / span > < span class = "token attr-name" > content< / span > < span class = "token attr-value" > < span class = "token punctuation attr-equals" > =< / span > < span class = "token punctuation" > "< / span > IE=edge< span class = "token punctuation" > "< / span > < / span > < span class = "token punctuation" > />< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > meta< / span > < span class = "token attr-name" > name< / span > < span class = "token attr-value" > < span class = "token punctuation attr-equals" > =< / span > < span class = "token punctuation" > "< / span > viewport< span class = "token punctuation" > "< / span > < / span > < span class = "token attr-name" > content< / span > < span class = "token attr-value" > < span class = "token punctuation attr-equals" > =< / span > < span class = "token punctuation" > "< / span > width=device-width, initial-scale=1.0< span class = "token punctuation" > "< / span > < / span > < span class = "token punctuation" > />< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > title< / span > < span class = "token punctuation" > >< / span > < / span > Document< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > title< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > head< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > body< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > ul< / span > < span class = "token attr-name" > id< / span > < span class = "token attr-value" > < span class = "token punctuation attr-equals" > =< / span > < span class = "token punctuation" > "< / span > app< span class = "token punctuation" > "< / span > < / span > < span class = "token punctuation" > >< / span > < / span > < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > ul< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > body< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > script< / span > < span class = "token punctuation" > >< / span > < / span > < span class = "token script" > < span class = "token language-javascript" >
< span class = "token keyword" > var< / span > arr < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span >
< span class = "token punctuation" > { < / span > < span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "小明"< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > age< / span > < span class = "token operator" > :< / span > < span class = "token number" > 11< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > sex< / span > < span class = "token operator" > :< / span > < span class = "token string" > "男"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span > < span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "小红"< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > age< / span > < span class = "token operator" > :< / span > < span class = "token number" > 22< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > sex< / span > < span class = "token operator" > :< / span > < span class = "token string" > "女"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > var< / span > listDOM < span class = "token operator" > =< / span > document< span class = "token punctuation" > .< / span > < span class = "token function" > getElementById< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "app"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
arr< span class = "token punctuation" > .< / span > < span class = "token function" > forEach< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > item< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > let< / span > _li < span class = "token operator" > =< / span > document< span class = "token punctuation" > .< / span > < span class = "token function" > createElement< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "li"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
_li< span class = "token punctuation" > .< / span > innerText < span class = "token operator" > =< / span > item< span class = "token punctuation" > .< / span > name< span class = "token punctuation" > ;< / span >
listDOM< span class = "token punctuation" > .< / span > < span class = "token function" > appendChild< / span > < span class = "token punctuation" > (< / span > _li< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< / span > < / span > < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > script< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > html< / span > < span class = "token punctuation" > >< / span > < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "mustache-原理" > < a href = "#mustache-原理" class = "headerlink" title = "mustache 原理" > < / a > mustache 原理< / h1 > < ul >
< li > 1、先把模板字符串编译成 tokens(代号)< / li >
< li > 2、根据 tokens， < / li >
< / ul >
< blockquote >
< p > 本质上， < code > 抽象语法树< / code > ， < code > 虚拟节点< / code > 的开山鼻祖< / p >
< / blockquote >
< p > 假设有这么一个模板字符串< / p >
< pre class = "line-numbers language-markup" data-language = "markup" > < code class = "language-markup" > < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > h1< / span > < span class = "token punctuation" > >< / span > < / span > 我买了一个{ { thing} } ,好{ { mood} } 啊< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > h1< / span > < span class = "token punctuation" > >< / span > < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < / span > < / code > < / pre >
< p > 会编译成 tokens， ： < / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // 这里面每一个数组行都是一个 token， < / span >
< span class = "token comment" > // html 标签也会被看成纯文本< / span >
< span class = "token punctuation" > [< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "< h1>我买了一个"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "name"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "thing"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "好"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "name"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "mood"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "啊< /h1>"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 当模板存在循环式，带层级嵌套，如下：< / p >
< pre class = "line-numbers language-markup" data-language = "markup" > < code class = "language-markup" > < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > div< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > ul< / span > < span class = "token punctuation" > >< / span > < / span >
{ { #arr} }
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > li< / span > < span class = "token punctuation" > >< / span > < / span > { { .} } < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > li< / span > < span class = "token punctuation" > >< / span > < / span >
{ { /arr} }
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > ul< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > div< / span > < span class = "token punctuation" > >< / span > < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 会被编译成< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token punctuation" > [< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "< div>< ul>"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span >
< span class = "token string" > "#"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token string" > "arr"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "li"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "name"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "."< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "< /li>"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "< /ul>< /div>"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 如果是双重循环，带层级嵌套继续加一层，例如：< / p >
< pre class = "line-numbers language-markup" data-language = "markup" > < code class = "language-markup" > < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > div< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > ol< / span > < span class = "token punctuation" > >< / span > < / span >
{ { #students} }
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > li< / span > < span class = "token punctuation" > >< / span > < / span >
学生{ { item.name} } 的爱好是
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > ol< / span > < span class = "token punctuation" > >< / span > < / span >
{ { #item.hobbies} }
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > li< / span > < span class = "token punctuation" > >< / span > < / span > { { .} } < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > li< / span > < span class = "token punctuation" > >< / span > < / span >
{ { /#item.hobbies} }
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > ol< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > li< / span > < span class = "token punctuation" > >< / span > < / span >
{ { /#students} }
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > ol< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > div< / span > < span class = "token punctuation" > >< / span > < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 会被编译成< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token punctuation" > [< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "< div>< ol>"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span >
< span class = "token string" > "#"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token string" > "students"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token keyword" > null< / span > < span class = "token punctuation" > ,< / span >
< span class = "token keyword" > null< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "< li>学生"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "name"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "name"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "的爱好是< ol>"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "#"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "hobbies"< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > null< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > null< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > 'text'< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > '< li>'< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > 'name'< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > '.'< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > 'text'< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > '< /li>'< / span > < span class = "token punctuation" > ]< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > 'text'< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > '< ol>< /li>'< /span>< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > 'text'< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > '< /ol>< /div>'< / span > < span class = "token punctuation" > ]< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< blockquote >
< p > 在< code > mustache.js< / code > 中完成上述这一过程的函数< code > parseTemplate< / code > ，可以去找源代码看< / p >
< / blockquote >
< h2 id = "tokens-生成算法" > < a href = "#tokens-生成算法" class = "headerlink" title = "tokens 生成算法" > < / a > tokens 生成算法< / h2 > < p > 用简单的模板字符串举例：< / p >
< pre class = "line-numbers language-markup" data-language = "markup" > < code class = "language-markup" > 我买了一个{ { thing} } ,好{ { mood} } 啊< span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < / span > < / code > < / pre >
< p > 有一个指针往右遍历，从< code > 我< / code > 开始，遍历到< code > 啊< / code > 结束，如下：< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > /**
*
* 我买了一个{ { thing} } ,好{ { mood} } 啊
* ↑
*
* Step1：
*
* 我买了一个{ { thing} } ,好{ { mood} } 啊
* ↑
*
* Step2：
*
* 我买了一个{ { thing} } ,好{ { mood} } 啊
* ↑
*
* Step3：
*
* 我买了一个{ { thing} } ,好{ { mood} } 啊
* ↑
*
* Step4：
*
* 我买了一个{ { thing} } ,好{ { mood} } 啊
* ↑
*
* Step5：
*
* 我买了一个{ { thing} } ,好{ { mood} } 啊
* ↑
*
* ... while(指针位置 >= 模板字符串.length)
*
* /< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< ul >
< li > Step1:< / li >
< / ul >
< p > 指针右移 1 个长度，以指针位置切割，字符串被分成< code > 我< / code > +< code > 买了一个{ { thing} } ,好{ { mood} } 啊< / code > < / p >
< ul >
< li > Step2:< / li >
< / ul >
< p > 指针右移 1 个长度，以指针位置切割，字符串被分成< code > 我买< / code > +< code > 了一个{ { thing} } ,好{ { mood} } 啊< / code > < / p >
< ul >
< li > Step3:< / li >
< / ul >
< p > 第一次遇到，通过 < code > indexOf(" { { ") == 0` 判断
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // 标记为 text 放到 tokens 中< / span >
token< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "我买了一个"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // tokens: [['text', '我买了一个']]< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < / span > < / code > < / pre >
结束，此时指针位置 = 4
- Step4:
指针右移 2 个长度，跳过`{ { `，暂存此时`pos_last = 6`
此时，右边字符串(尾字符串)`thing} } ,好{ { mood} } 啊< / code > < / p >
< p > 右移 5 个长度，识别< code > 模板内部数据对象< / code > ： < / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token function" > substring< / span > < span class = "token punctuation" > (< / span > post_last< span class = "token punctuation" > ,< / span > < span class = "token number" > 6< / span > < span class = "token operator" > +< / span > < span class = "token number" > 5< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // thing 5个长度< / span >
< span class = "token comment" > // 标记为 name 放到 tokens 中< / span >
token< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "name"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "thing"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // tokens: [['text', '我买了一个']], ['name', 'thing']]< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 结束，此时指针位置 = 11< / p >
< ul >
< li > Step5:< / li >
< / ul >
< blockquote >
< p > 遇到 < code > } } < / code > ，通过 < code > indexOf(" } } " ) == 0< / code > 判断< / p >
< / blockquote >
< p > 指针右移 2 个长度，跳过< code > } } < / code > ，暂存此时< code > post_last = 13< / code > ，继续右移 2 个长度< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token function" > substring< / span > < span class = "token punctuation" > (< / span > post_last< span class = "token punctuation" > ,< / span > < span class = "token number" > 13< / span > < span class = "token operator" > +< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // ,好 2个长度< / span >
< span class = "token comment" > // 标记为 text 放到 tokens 中< / span >
token< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > ",好"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // tokens: [['text', '我买了一个']], ['name', 'thing'],['text', ',好' ]]< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< blockquote >
< p > 第二次，遇到 < code > { { `
剩下循环执行就行了，这个过程，我们可以称作`扫描 Scan`
## 扫描器 Scanner
新建一个 `Scanner.js`，用来扫描模板字符串，实现上面的原理
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > /**
* 模板字符串扫描器
*/< / span >
< span class = "token keyword" > class< / span > < span class = "token class-name" > Scanner< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > constructor< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > templ< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > templ < span class = "token operator" > =< / span > templ< span class = "token punctuation" > ;< / span > < span class = "token comment" > // 模板字符串< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > tail < span class = "token operator" > =< / span > templ< span class = "token punctuation" > ;< / span > < span class = "token comment" > // 尾字符串< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > pPos < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 指针位置< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 指针跳过模板标签
* @param { 模板语法包围标签} tag
*/< / span >
< span class = "token function" > jumpTag< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > tag< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > tail< span class = "token punctuation" > .< / span > < span class = "token function" > indexOf< / span > < span class = "token punctuation" > (< / span > tag< span class = "token punctuation" > )< / span > < span class = "token operator" > ===< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > pPos < span class = "token operator" > +=< / span > tag< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span > < span class = "token comment" > // 指针右移 tag.length 个长度< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > tail < span class = "token operator" > =< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > templ< span class = "token punctuation" > .< / span > < span class = "token function" > substring< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > pPos< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 尾字符串更新< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 指针遇见模板标签 { {
* @param { 模板语法包围标签} tag
*/< / span >
< span class = "token function" > missTag< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > tag< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > let< / span > pPos_last < span class = "token operator" > =< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > pPos< span class = "token punctuation" > ;< / span >
< span class = "token keyword" > while< / span > < span class = "token punctuation" > (< / span > < span class = "token operator" > !< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > eof< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > & & < / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > tail< span class = "token punctuation" > .< / span > < span class = "token function" > indexOf< / span > < span class = "token punctuation" > (< / span > tag< span class = "token punctuation" > )< / span > < span class = "token operator" > !==< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > pPos< span class = "token operator" > ++< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > tail < span class = "token operator" > =< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > templ< span class = "token punctuation" > .< / span > < span class = "token function" > substring< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > pPos< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > templ< span class = "token punctuation" > .< / span > < span class = "token function" > substring< / span > < span class = "token punctuation" > (< / span > pPos_last< span class = "token punctuation" > ,< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > pPos< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token function" > eof< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > pPos < span class = "token operator" > >=< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > templ< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
## 分析器 Parser
调用`Scanner.js`
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > tmpl < span class = "token operator" > =< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > 我买了一个{ { thing} } ,好{ { mood} } 啊< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 编译 模板字符串 => tokens< / span >
< span class = "token keyword" > const< / span > Parser < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token function-variable function" > createTokens< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > tmpl< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > let< / span > scanner < span class = "token operator" > =< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Scanner< / span > < span class = "token punctuation" > (< / span > tmpl< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > tokens < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // scanner 循环执行< / span >
< span class = "token keyword" > while< / span > < span class = "token punctuation" > (< / span > < span class = "token operator" > !< / span > scanner< span class = "token punctuation" > .< / span > < span class = "token function" > eof< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
ctx < span class = "token operator" > =< / span > scanner< span class = "token punctuation" > .< / span > < span class = "token function" > missTag< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "{ { "< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 返回 头字符串< / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > ctx < span class = "token operator" > !=< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
tokens< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > ctx< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
scanner< span class = "token punctuation" > .< / span > < span class = "token function" > jumpTag< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "{ { "< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 跳过 模板字符< / span >
ctx < span class = "token operator" > =< / span > scanner< span class = "token punctuation" > .< / span > < span class = "token function" > missTag< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "} } "< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 返回 { { x } } < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > ctx < span class = "token operator" > !=< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
tokens< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "name"< / span > < span class = "token punctuation" > ,< / span > ctx< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
scanner< span class = "token punctuation" > .< / span > < span class = "token function" > jumpTag< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "} } "< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > tokens< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > Parser< span class = "token punctuation" > .< / span > < span class = "token function" > createTokens< / span > < span class = "token punctuation" > (< / span > tmpl< span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 输出，非常的 奈一丝< / span >
< span class = "token comment" > // ["text", "我买了一个"]< / span >
< span class = "token comment" > // ["name", "thing"]< / span >
< span class = "token comment" > // ["text", ",好"]< / span >
< span class = "token comment" > // ["name", "mood"]< / span >
< span class = "token comment" > // ["text", "啊"]< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
## 扫描器 Scanner 增强
上面的`Parser`只能识别`{ { `和`} } < / code > ，如果模板语法复杂一点，比如加入 < code > { { #list} } ...{ { /list} } < / code > ，需要增强< code > Parser< / code > < / p >
< / blockquote >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > const< / span > template < span class = "token operator" > =< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" >
哈哈哈
{ { #students} }
我买了一个 { { thing } } ,好{ { mood} } 啊{ { a} }
{ { item.name} }
{ { /students} }
< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > const< / span > Parser < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token function-variable function" > createTokens< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > tmpl< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > let< / span > scanner < span class = "token operator" > =< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Scanner< / span > < span class = "token punctuation" > (< / span > tmpl< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > tokens < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > ctx < span class = "token operator" > =< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // scanner 循环执行< / span >
< span class = "token keyword" > while< / span > < span class = "token punctuation" > (< / span > < span class = "token operator" > !< / span > scanner< span class = "token punctuation" > .< / span > < span class = "token function" > eof< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
ctx < span class = "token operator" > =< / span > scanner< span class = "token punctuation" > .< / span > < span class = "token function" > missTag< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "{ { "< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 返回 头字符串< / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > ctx < span class = "token operator" > !=< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
tokens< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "text"< / span > < span class = "token punctuation" > ,< / span > ctx< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
scanner< span class = "token punctuation" > .< / span > < span class = "token function" > jumpTag< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "{ { "< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 跳过 模板字符< / span >
ctx < span class = "token operator" > =< / span > scanner< span class = "token punctuation" > .< / span > < span class = "token function" > missTag< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "} } "< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 返回 { { x } } < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > ctx < span class = "token operator" > !=< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > switch< / span > < span class = "token punctuation" > (< / span > ctx< span class = "token punctuation" > [< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > case< / span > < span class = "token string" > "#"< / span > < span class = "token operator" > :< / span >
tokens< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "#"< / span > < span class = "token punctuation" > ,< / span > ctx< span class = "token punctuation" > .< / span > < span class = "token function" > substr< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // { { # x } } < / span >
< span class = "token keyword" > break< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > case< / span > < span class = "token string" > "/"< / span > < span class = "token operator" > :< / span >
tokens< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "/"< / span > < span class = "token punctuation" > ,< / span > ctx< span class = "token punctuation" > .< / span > < span class = "token function" > substr< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > break< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > default< / span > < span class = "token operator" > :< / span >
tokens< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "name"< / span > < span class = "token punctuation" > ,< / span > ctx< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > break< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span >
scanner< span class = "token punctuation" > .< / span > < span class = "token function" > jumpTag< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "} } "< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > tokens< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > Parser< span class = "token punctuation" > .< / span > < span class = "token function" > createTokens< / span > < span class = "token punctuation" > (< / span > template< span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 输出< / span >
< span class = "token comment" > // ["text", "↵ 哈哈哈↵ "]< / span >
< span class = "token comment" > // ["#", "students"]< / span >
< span class = "token comment" > // ["text", "↵ 我买了一个 "]< / span >
< span class = "token comment" > // ["name", " thing "]< / span >
< span class = "token comment" > // ["text", ",好"]< / span >
< span class = "token comment" > // ["name", "mood"]< / span >
< span class = "token comment" > // ["text", "啊"]< / span >
< span class = "token comment" > // ["name", "a"]< / span >
< span class = "token comment" > // ["text", "↵ "]< / span >
< span class = "token comment" > // ["name", "item.name"]< / span >
< span class = "token comment" > // ["text", "↵ "]< / span >
< span class = "token comment" > // ["/", "students"]< / span >
< span class = "token comment" > // ["text", "↵ "]< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "栈队列算法" > < a href = "#栈队列算法" class = "headerlink" title = "栈队列算法" > < / a > 栈队列算法< / h2 > < p > 上一步最后的输出，只有单层嵌套，如果是两层嵌套怎么办？< / p >
< p > 例如模板语法如下：< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > var< / span > template < span class = "token operator" > =< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" >
哈哈哈
{ { #students} }
{ { #stu} }
{ { stu.name} } 买了一个 { { thing } } ,好{ { mood} } 啊{ { a} }
{ { /stu} }
{ { item.name} }
{ { /students} }
< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 经过< code > Parser< / code > 处理得到：< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > /**
*
* ["text", "↵ 哈哈哈↵ "]
* ["#", "students"]
* ["text", "↵ "]
* ["#", "stu"]
* ["text", "↵ "]
* ["name", "stu.name"]
* ["text", "买了一个 "]
* ["name", " thing "]
* ["text", ",好"]
* ["name", "mood"]
* ["text", "啊"]
* ["name", "a"]
* ["text", "↵ "]
* ["/", "stu"]
* ["text", "↵ "]
* ["name", "item.name"]
* ["text", "↵ "]
* ["/", "students"]
* ["text", "↵ "]
*
* /< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 此时< code > students< / code > 和< code > stu< / code > 都是< code > #< / code > 标记，我们需要利用算法处理他们的嵌套结构，处理成大约如下这样的结构：< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > /**
*
* ["text", "↵ 哈哈哈↵ "]
* Array(3)
* "#"
* "students"
* Array(5)
* ["text", "↵ "]
* ["#", "stu", Array(9)]
* ["text", "↵ "]
* ["name", "item.name"]
* ["text", "↵ "]
* ["text", "↵ "]
*
* /< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "常用工具类" > < a href = "#常用工具类" class = "headerlink" title = "常用工具类" > < / a > 常用工具类< / h1 > < h2 id = "递归" > < a href = "#递归" class = "headerlink" title = "递归" > < / a > 递归< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > /**
* { string} dir 递归根目录
* { object} list 暂存参数
*/< / span >
< span class = "token keyword" > const< / span > < span class = "token function-variable function" > deep< / span > < span class = "token operator" > =< / span > < span class = "token keyword" > async< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > dir< span class = "token punctuation" > ,< / span > list < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > const< / span > dirs < span class = "token operator" > =< / span > < span class = "token keyword" > await< / span > fs< span class = "token punctuation" > .< / span > promises< span class = "token punctuation" > .< / span > < span class = "token function" > readdir< / span > < span class = "token punctuation" > (< / span > dir< span class = "token punctuation" > )< / span >
< span class = "token keyword" > for< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > let< / span > i < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span > i < span class = "token operator" > < < / span > dirs< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span > i< span class = "token operator" > ++< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > const< / span > item < span class = "token operator" > =< / span > dirs< span class = "token punctuation" > [< / span > i< span class = "token punctuation" > ]< / span >
< span class = "token keyword" > const< / span > itemPath < span class = "token operator" > =< / span > path< span class = "token punctuation" > .< / span > < span class = "token function" > join< / span > < span class = "token punctuation" > (< / span > dir< span class = "token punctuation" > ,< / span > item< span class = "token punctuation" > )< / span >
< span class = "token keyword" > const< / span > isDir < span class = "token operator" > =< / span > fs< span class = "token punctuation" > .< / span > < span class = "token function" > statSync< / span > < span class = "token punctuation" > (< / span > itemPath< span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > isDirectory< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span >
isDir < span class = "token operator" > ?< / span > < span class = "token keyword" > await< / span > < span class = "token function" > deep< / span > < span class = "token punctuation" > (< / span > itemPath< span class = "token punctuation" > ,< / span > list< span class = "token punctuation" > )< / span > < span class = "token operator" > :< / span > list< span class = "token punctuation" > .< / span > < span class = "token function" > push< / span > < span class = "token punctuation" > (< / span > itemPath< span class = "token punctuation" > )< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > list
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "自增id短码" > < a href = "#自增id短码" class = "headerlink" title = "自增id短码" > < / a > 自增id短码< / h2 > < p > 用于连接分享< / p >
< pre class = "line-numbers language-typescript" data-language = "typescript" > < code class = "language-typescript" > < span class = "token keyword" > const< / span > < span class = "token function-variable function" > createAscString< / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > id< span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > const< / span > dictionary < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span >
< span class = "token string" > "0123456789"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token string" > "abcdefghigklmnopqrstuvwxyz"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token string" > "ABCDEFGHIGKLMNOPQRSTUVWXYZ"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > chars < span class = "token operator" > =< / span > dictionary< span class = "token punctuation" > .< / span > < span class = "token function" > join< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > split< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ,< / span >
radix < span class = "token operator" > =< / span > chars< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ,< / span >
qutient < span class = "token operator" > =< / span > < span class = "token number" > 1000< / span > < span class = "token operator" > *< / span > < span class = "token number" > 1000< / span > < span class = "token operator" > *< / span > < span class = "token number" > 9999< / span > < span class = "token operator" > +< / span > < span class = "token operator" > +< / span > id< span class = "token punctuation" > ,< / span >
arr < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > while< / span > < span class = "token punctuation" > (< / span > qutient< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
mod < span class = "token operator" > =< / span > qutient < span class = "token operator" > %< / span > radix< span class = "token punctuation" > ;< / span >
qutient < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > qutient < span class = "token operator" > -< / span > mod< span class = "token punctuation" > )< / span > < span class = "token operator" > /< / span > radix< span class = "token punctuation" > ;< / span >
arr< span class = "token punctuation" > .< / span > < span class = "token function" > unshift< / span > < span class = "token punctuation" > (< / span > chars< span class = "token punctuation" > [< / span > mod< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > arr< span class = "token punctuation" > .< / span > < span class = "token function" > join< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token builtin" > console< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token function" > createAscString< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > 100000000< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "手动实现-eventBus" > < a href = "#手动实现-eventBus" class = "headerlink" title = "手动实现 eventBus" > < / a > 手动实现 eventBus< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > export< / span > < span class = "token keyword" > default< / span > < span class = "token keyword" > class< / span > < span class = "token class-name" > EventBus< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > constructor< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // key-value : eventName-date< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > callbacks < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 监听事件
* @param { 事件名} eventName
* @param { 回调函数} callback
*/< / span >
< span class = "token function" > on< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > eventName< span class = "token punctuation" > ,< / span > callback< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > checkType< / span > < span class = "token punctuation" > (< / span > eventName< span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > callbacks< span class = "token punctuation" > [< / span > eventName< span class = "token punctuation" > ]< / span >
< span class = "token operator" > ?< / span > < span class = "token function" > callback< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > callbacks< span class = "token punctuation" > [< / span > eventName< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span >
< span class = "token operator" > :< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > error< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > The event has not been declared< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 注册一个事件
* @param { 事件名} eventName
* @param { 传递的对象} data
*/< / span >
< span class = "token function" > emit< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > eventName< span class = "token punctuation" > ,< / span > data< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > checkType< / span > < span class = "token punctuation" > (< / span > eventName< span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > callbacks< span class = "token punctuation" > [< / span > eventName< span class = "token punctuation" > ]< / span > < span class = "token operator" > =< / span > data< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 注销事件，不传参数默认注销全部事件
* @param { 事件名} eventName
*/< / span >
< span class = "token function" > off< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > eventName< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
eventName
< span class = "token operator" > ?< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > checkType< / span > < span class = "token punctuation" > (< / span > eventName< span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > removeEvent< / span > < span class = "token punctuation" > (< / span > eventName< span class = "token punctuation" > )< / span >
< span class = "token operator" > :< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > emptyEvent< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 移出事件
* @param { 事件名} eventName
*/< / span >
< span class = "token function" > removeEvent< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > eventName< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
Reflect< span class = "token punctuation" > .< / span > < span class = "token function" > deleteProperty< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > callbacks< span class = "token punctuation" > ,< / span > eventName< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 清空全部事件
*/< / span >
< span class = "token function" > emptyEvent< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > callbacks < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 参数类型校验
* @param { 参数} param
* @param { 合法的类型} validType
*/< / span >
< span class = "token function" > checkType< / span > < span class = "token punctuation" > (< / span > param< span class = "token punctuation" > ,< / span > validType < span class = "token operator" > =< / span > < span class = "token string" > "string"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > typeof< / span > param < span class = "token operator" > !==< / span > validType< span class = "token punctuation" > )< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > error< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > (param, < / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > param< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > ) should be of < / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > validType< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > type< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 缅怀jQ链式调用< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > /**
* 错误提示
* @param { 提示文字} text
*/< / span >
< span class = "token function" > error< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > text< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > throw< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Error< / span > < span class = "token punctuation" > (< / span > text< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 调用< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // 省略import< / span >
< span class = "token keyword" > const< / span > eventBus < span class = "token operator" > =< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > EventBus< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
eventBus< span class = "token punctuation" > .< / span > < span class = "token function" > emit< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "login"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > a< / span > < span class = "token operator" > :< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > d< / span > < span class = "token operator" > :< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
eventBus< span class = "token punctuation" > .< / span > < span class = "token function" > on< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > 123< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > d< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > d< span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // [{ ...} ]< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "判断对象是否有某个-key" > < a href = "#判断对象是否有某个-key" class = "headerlink" title = "判断对象是否有某个 key" > < / a > 判断对象是否有某个 key< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > obj < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > alias< / span > < span class = "token operator" > :< / span > < span class = "token string" > "es6"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token string" > "alias"< / span > < span class = "token keyword" > in< / span > obj< span class = "token punctuation" > ;< / span > < span class = "token comment" > // true< / span >
Reflect< span class = "token punctuation" > .< / span > < span class = "token function" > has< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > ,< / span > < span class = "token string" > "alias"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // true< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "浏览器" > < a href = "#浏览器" class = "headerlink" title = "浏览器" > < / a > 浏览器< / h2 > < h2 id = "版本信息" > < a href = "#版本信息" class = "headerlink" title = "版本信息" > < / a > 版本信息< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > window< span class = "token punctuation" > .< / span > navigator< span class = "token punctuation" > .< / span > userAgent< span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < / span > < / code > < / pre >
< h2 id = "兼容事件绑定" > < a href = "#兼容事件绑定" class = "headerlink" title = "兼容事件绑定" > < / a > 兼容事件绑定< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > /*
兼容低版本IE， ，
eventName为事件名（ ， ） ，
*/< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > addEvent< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > ele< span class = "token punctuation" > ,< / span > eventName< span class = "token punctuation" > ,< / span > fun< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
ele< span class = "token punctuation" > .< / span > addEventListener
< span class = "token operator" > ?< / span > ele< span class = "token punctuation" > .< / span > < span class = "token function" > addEventListener< / span > < span class = "token punctuation" > (< / span > eventName< span class = "token punctuation" > ,< / span > fun< span class = "token punctuation" > ,< / span > < span class = "token boolean" > false< / span > < span class = "token punctuation" > )< / span >
< span class = "token operator" > :< / span > ele< span class = "token punctuation" > .< / span > < span class = "token function" > attachEvent< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "on"< / span > < span class = "token operator" > +< / span > eventNme< span class = "token punctuation" > ,< / span > fun< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "数组对象" > < a href = "#数组对象" class = "headerlink" title = "数组对象" > < / a > 数组对象< / h2 > < h2 id = "reduce" > < a href = "#reduce" class = "headerlink" title = "reduce" > < / a > reduce< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > var< / span > arr < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 3< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > var< / span > sum < span class = "token operator" > =< / span > arr< span class = "token punctuation" > .< / span > < span class = "token function" > reduce< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > prev< span class = "token punctuation" > ,< / span > cur< span class = "token punctuation" > ,< / span > index< span class = "token punctuation" > ,< / span > arr< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > prev< span class = "token punctuation" > ,< / span > cur< span class = "token punctuation" > ,< / span > index< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > prev < span class = "token operator" > +< / span > cur< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > ， < span class = "token number" > 0< / span > < span class = "token punctuation" > )< / span > < span class = "token comment" > //注意这里设置了初始值< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > arr< span class = "token punctuation" > ,< / span > sum< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 求和< / span >
< span class = "token keyword" > const< / span > sum < span class = "token operator" > =< / span > arr< span class = "token punctuation" > .< / span > < span class = "token function" > reduce< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > p< span class = "token punctuation" > ,< / span > c< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > p< span class = "token operator" > +< / span > c< span class = "token punctuation" > )< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "对象内部根据-key-对-value-进行排序-取前-3" > < a href = "#对象内部根据-key-对-value-进行排序-取前-3" class = "headerlink" title = "对象内部根据 key 对 value 进行排序,取前 3" > < / a > 对象内部根据 key 对 value 进行排序,取前 3< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > datasource < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span >
< span class = "token punctuation" > { < / span > < span class = "token literal-property property" > price< / span > < span class = "token operator" > :< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > alias< / span > < span class = "token operator" > :< / span > < span class = "token string" > "watermelon"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span > < span class = "token literal-property property" > price< / span > < span class = "token operator" > :< / span > < span class = "token number" > 3< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > alias< / span > < span class = "token operator" > :< / span > < span class = "token string" > "orange"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span > < span class = "token literal-property property" > price< / span > < span class = "token operator" > :< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > alias< / span > < span class = "token operator" > :< / span > < span class = "token string" > "banana"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span > < span class = "token literal-property property" > price< / span > < span class = "token operator" > :< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > ,< / span > < span class = "token literal-property property" > alias< / span > < span class = "token operator" > :< / span > < span class = "token string" > "apple"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 降序排列< / span >
< span class = "token keyword" > let< / span > < span class = "token function-variable function" > compare< / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > key< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > a< span class = "token punctuation" > ,< / span > b< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > b< span class = "token punctuation" > [< / span > key< span class = "token punctuation" > ]< / span > < span class = "token operator" > -< / span > a< span class = "token punctuation" > [< / span > key< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > sorted < span class = "token operator" > =< / span > datasource
< span class = "token punctuation" > .< / span > < span class = "token function" > sort< / span > < span class = "token punctuation" > (< / span > < span class = "token function" > compare< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "price"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span >
< span class = "token punctuation" > .< / span > < span class = "token function" > slice< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 3< / span > < span class = "token punctuation" > )< / span >
< span class = "token punctuation" > .< / span > < span class = "token function" > map< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > i< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > i< span class = "token punctuation" > [< / span > < span class = "token string" > "alias"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 返回 ["apple", "orange", "banana"]< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "随机字符串" > < a href = "#随机字符串" class = "headerlink" title = "随机字符串" > < / a > 随机字符串< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > const< / span > < span class = "token function-variable function" > getRandomRangeNum< / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > len < span class = "token operator" > =< / span > < span class = "token number" > 32< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // 略去不宜辨识字符< / span >
< span class = "token keyword" > let< / span > dictionary < span class = "token operator" > =< / span > < span class = "token string" > "ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz"< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > maxPos < span class = "token operator" > =< / span > dictionary< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > res < span class = "token operator" > =< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > for< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > let< / span > i < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span > i < span class = "token operator" > < < / span > len< span class = "token punctuation" > ;< / span > i< span class = "token operator" > ++< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
res < span class = "token operator" > +=< / span > dictionary< span class = "token punctuation" > .< / span > < span class = "token function" > charAt< / span > < span class = "token punctuation" > (< / span > Math< span class = "token punctuation" > .< / span > < span class = "token function" > floor< / span > < span class = "token punctuation" > (< / span > Math< span class = "token punctuation" > .< / span > < span class = "token function" > random< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > *< / span > maxPos< span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > res< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "类型检测" > < a href = "#类型检测" class = "headerlink" title = "类型检测" > < / a > 类型检测< / h2 > < p > Q： < code > typeof foo === " object" < / code > 检测< code > foo< / code > 是否为对象有什么缺点？如何避免？< / p >
< p > A： < code > typeof< / code > 是否能准确判断一个对象变量，答案是否定的，< code > null< / code > 的结果也是 < code > object< / code > ， < code > Array< / code > 的结果也是 < code > object< / code > ，有时候我们需要的是 “纯粹” 的 < code > object< / code > 对象< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token class-name" > Object< / span > < span class = "token punctuation" > .< / span > prototype< span class = "token punctuation" > .< / span > < span class = "token function" > toString< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > call< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > )< / span > < span class = "token operator" > ===< / span > < span class = "token string" > "[object Object]"< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < / span > < / code > < / pre >
< h2 id = "倒计时" > < a href = "#倒计时" class = "headerlink" title = "倒计时" > < / a > 倒计时< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > class< / span > < span class = "token class-name" > Countdown< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > constructor< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > startNum< span class = "token punctuation" > ,< / span > endNum< span class = "token punctuation" > ,< / span > interval< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token punctuation" > [< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > startNum< span class = "token punctuation" > ,< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > endNum< span class = "token punctuation" > ,< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > interval< span class = "token punctuation" > ]< / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > startNum< span class = "token punctuation" > ,< / span > endNum< span class = "token punctuation" > ,< / span > interval< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token function" > execute< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > var< / span > timer < span class = "token operator" > =< / span > < span class = "token function" > setTimeout< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > startNum < span class = "token operator" > >=< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > endNum< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > startNum< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > startNum < span class = "token operator" > -=< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > execute< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token keyword" > else< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > clearTimeout< / span > < span class = "token punctuation" > (< / span > timer< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > interval< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // 实例化调用< / span >
< span class = "token keyword" > var< / span > countdown < span class = "token operator" > =< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Countdown< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > 5< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 1000< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > execute< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "范围随机数" > < a href = "#范围随机数" class = "headerlink" title = "范围随机数" > < / a > 范围随机数< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // 能取到 min， < / span >
< span class = "token keyword" > function< / span > < span class = "token function" > getRandomRangeNum< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > min< span class = "token punctuation" > ,< / span > max< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > min < span class = "token operator" > +< / span > Math< span class = "token punctuation" > .< / span > < span class = "token function" > floor< / span > < span class = "token punctuation" > (< / span > Math< span class = "token punctuation" > .< / span > < span class = "token function" > random< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > *< / span > < span class = "token punctuation" > (< / span > max < span class = "token operator" > -< / span > min< span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "获取当前月的天数" > < a href = "#获取当前月的天数" class = "headerlink" title = "获取当前月的天数" > < / a > 获取当前月的天数< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > const< / span > getCurMonthDays < span class = "token operator" > =< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Date< / span > < span class = "token punctuation" > (< / span >
< span class = "token keyword" > new< / span > < span class = "token class-name" > Date< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > getFullYear< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ,< / span >
< span class = "token keyword" > new< / span > < span class = "token class-name" > Date< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > getMonth< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > +< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ,< / span >
< span class = "token number" > 0< / span >
< span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > getDate< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "对象小操作" > < a href = "#对象小操作" class = "headerlink" title = "对象小操作" > < / a > 对象小操作< / h1 > < h2 id = "去虚假值" > < a href = "#去虚假值" class = "headerlink" title = "去虚假值" > < / a > 去虚假值< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > arr4 < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "小明"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "小蓝"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > ""< / span > < span class = "token punctuation" > ,< / span > < span class = "token boolean" > false< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > " "< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > undefined< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > null< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > NaN< / span > < span class = "token punctuation" > ,< / span > < span class = "token boolean" > true< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > arr4< span class = "token punctuation" > .< / span > < span class = "token function" > filter< / span > < span class = "token punctuation" > (< / span > Boolean< span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // => ['小明', '小蓝', ' ', true]< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "头尾插入" > < a href = "#头尾插入" class = "headerlink" title = "头尾插入" > < / a > 头尾插入< / h2 > < p > 效率比 < code > unshift()< / code > 高< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > arr < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 3< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 头插入< / span >
< span class = "token punctuation" > [< / span > < span class = "token string" > "haha"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > concat< / span > < span class = "token punctuation" > (< / span > arr< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 尾插入< / span >
arr< span class = "token punctuation" > .< / span > < span class = "token function" > concat< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "haha"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "删除属性" > < a href = "#删除属性" class = "headerlink" title = "删除属性" > < / a > 删除属性< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > deleteA< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > obj< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > delete< / span > obj< span class = "token punctuation" > .< / span > < span class = "token constant" > A< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > obj< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // 使用解构赋值< / span >
< span class = "token keyword" > const< / span > < span class = "token function-variable function" > deleteA< / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > < span class = "token punctuation" > { < / span > < span class = "token constant" > A< / span > < span class = "token punctuation" > ,< / span > < span class = "token operator" > ...< / span > rest < span class = "token punctuation" > } < / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > rest< span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "生产、加工、消费分离" > < a href = "#生产、加工、消费分离" class = "headerlink" title = "生产、加工、消费分离" > < / a > 生产、加工、消费分离< / h1 > < ul >
< li > 从接口拿数据到视图 fetch api< / li >
< li > 加工 computed< / li >
< li > 消费 v-for< / li >
< / ul >
< h1 id = "元数据" > < a href = "#元数据" class = "headerlink" title = "元数据" > < / a > 元数据< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > import< / span > < span class = "token string" > "reflect-metadata"< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // npm install reflect-metadata< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > Role< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > < span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > string< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > :< / span > ClassDecorator < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > target< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
Reflect< span class = "token punctuation" > .< / span > < span class = "token function" > defineMetadata< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "role"< / span > < span class = "token punctuation" > ,< / span > name< span class = "token punctuation" > ,< / span > target< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
@< span class = "token function" > Role< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "admin"< / span > < span class = "token punctuation" > )< / span >
< span class = "token keyword" > class< / span > < span class = "token class-name" > Post< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span >
< span class = "token keyword" > const< / span > metadata < span class = "token operator" > =< / span > Reflect< span class = "token punctuation" > .< / span > < span class = "token function" > getMetadata< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "role"< / span > < span class = "token punctuation" > ,< / span > Post< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
Reflect< span class = "token punctuation" > .< / span > < span class = "token function" > set< / span > < span class = "token punctuation" > (< / span > Post< span class = "token punctuation" > ,< / span > < span class = "token string" > "role2"< / span > < span class = "token punctuation" > ,< / span > metadata< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > Reflect< span class = "token punctuation" > .< / span > < span class = "token function" > get< / span > < span class = "token punctuation" > (< / span > Post< span class = "token punctuation" > ,< / span > < span class = "token string" > "role2"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // admin< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "防抖与节流" > < a href = "#防抖与节流" class = "headerlink" title = "防抖与节流" > < / a > 防抖与节流< / h1 > < p > 在页面上监听诸如< code > scroll< / code > （页面滚动），< code > mousemove< / code > （鼠标移动） ， < code > keydown< / code > ， < code > keyup< / code > ， < code > keypress< / code > （按下键盘）等等一系列事件的时候，我们并不希望频繁的触发这类监听，尤其当请求非常消耗资源时，这种操作会导致服务器性能急剧下降。< / p >
< h2 id = "Debounce" > < a href = "#Debounce" class = "headerlink" title = "Debounce" > < / a > Debounce< / h2 > < p > 把触发非常频繁的事件合并成一次延迟执行，如果对监听函数使用 100ms 的容忍时间，那么时间在第 3.1s 的时候执行< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // 默认延时100ms< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > debounce< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > func< span class = "token punctuation" > ,< / span > dealy < span class = "token operator" > =< / span > < span class = "token number" > 100< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > let< / span > timer< span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // 暂存this和参数< / span >
< span class = "token keyword" > let< / span > _this < span class = "token operator" > =< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > args < span class = "token operator" > =< / span > arguments< span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 清除定时器， < / span >
< span class = "token function" > clearTimeout< / span > < span class = "token punctuation" > (< / span > timer< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
timer < span class = "token operator" > =< / span > < span class = "token function" > setTimeout< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > func< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > apply< / span > < span class = "token punctuation" > (< / span > _this< span class = "token punctuation" > ,< / span > args< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span > dealy< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // 执行函数< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > handler< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > delay 100ms ,then handle< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // dom添加监听< / span >
document
< span class = "token punctuation" > .< / span > < span class = "token function" > querySelector< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "#someNode"< / span > < span class = "token punctuation" > )< / span >
< span class = "token punctuation" > .< / span > < span class = "token function" > addEventListener< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "scroll"< / span > < span class = "token punctuation" > ,< / span > < span class = "token function" > debounce< / span > < span class = "token punctuation" > (< / span > handler< span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "Throttle" > < a href = "#Throttle" class = "headerlink" title = "Throttle" > < / a > Throttle< / h2 > < p > 固定函数执行的速率，即所谓的“节流”。设置一个阀值，在阀值内，把触发的事件合并成一次执行；当到达阀值，必定执行一次事件。< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > throttle< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > func< span class = "token punctuation" > ,< / span > delay< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > let< / span > statTime < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > let< / span > currentTime < span class = "token operator" > =< / span > < span class = "token operator" > +< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Date< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > currentTime < span class = "token operator" > -< / span > statTime < span class = "token operator" > >< / span > delay< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > func< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > apply< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > ,< / span > arguments< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
statTime < span class = "token operator" > =< / span > currentTime< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // 执行函数< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > resizeHandler< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > resize< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // window添加监听< / span >
window< span class = "token punctuation" > .< / span > onresize < span class = "token operator" > =< / span > < span class = "token function" > throttle< / span > < span class = "token punctuation" > (< / span > resizeHandler< span class = "token punctuation" > ,< / span > < span class = "token number" > 300< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "this-指向" > < a href = "#this-指向" class = "headerlink" title = "this 指向" > < / a > this 指向< / h1 > < h2 id = "全局环境" > < a href = "#全局环境" class = "headerlink" title = "全局环境" > < / a > 全局环境< / h2 > < p > 全局环境下， （ ） ， < / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token operator" > ===< / span > window< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // true< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > a < span class = "token operator" > =< / span > < span class = "token number" > 37< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > window< span class = "token punctuation" > .< / span > a< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 37< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "函数上下文调用" > < a href = "#函数上下文调用" class = "headerlink" title = "函数上下文调用" > < / a > 函数上下文调用< / h2 > < ul >
< li > 非严格模式< / li >
< / ul >
< p > 没有被上一级的对象所调用, this 默认指向全局对象 window< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > f1< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token function" > f1< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > ===< / span > window< span class = "token punctuation" > ;< / span > < span class = "token comment" > // true< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< ul >
< li > 严格模式< / li >
< / ul >
< p > this 指向 undefined< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > f2< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token string" > "use strict"< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 这里是严格模式< / span >
< span class = "token keyword" > return< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token function" > f2< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > ===< / span > < span class = "token keyword" > undefined< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // true< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "箭头函数" > < a href = "#箭头函数" class = "headerlink" title = "箭头函数" > < / a > 箭头函数< / h2 > < blockquote >
< p > 箭头函数中， < / p >
< / blockquote >
< p > 在全局代码中，箭头函数被设置为全局对象，总之箭头函数不改变 this 指向< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > var< / span > globalObject < span class = "token operator" > =< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > var< / span > < span class = "token function-variable function" > foo< / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token function" > foo< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > ===< / span > globalObject< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // true< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 箭头函数作为对象的方法使用，指向全局 window 对象< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > var< / span > obj < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > i< / span > < span class = "token operator" > :< / span > < span class = "token number" > 10< / span > < span class = "token punctuation" > ,< / span >
< span class = "token function-variable function" > b< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > i< span class = "token punctuation" > ,< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ,< / span >
< span class = "token function-variable function" > c< / span > < span class = "token operator" > :< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > i< span class = "token punctuation" > ,< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
obj< span class = "token punctuation" > .< / span > < span class = "token function" > b< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // undefined window{ ...} < / span >
obj< span class = "token punctuation" > .< / span > < span class = "token function" > c< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 10 Object { ...} < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 箭头函数可以让 this 指向固化，这种特性很有利于封装回调函数< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // 总是指向 handler 对象。如果不使用箭头函数则指向全局 document 对象< / span >
< span class = "token keyword" > var< / span > handler < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > id< / span > < span class = "token operator" > :< / span > < span class = "token string" > "123456"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token function-variable function" > init< / span > < span class = "token operator" > :< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
document< span class = "token punctuation" > .< / span > < span class = "token function" > addEventListener< / span > < span class = "token punctuation" > (< / span >
< span class = "token string" > "click"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > (< / span > < span class = "token parameter" > event< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > doSomething< / span > < span class = "token punctuation" > (< / span > event< span class = "token punctuation" > .< / span > type< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ,< / span >
< span class = "token boolean" > false< / span >
< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token function-variable function" > doSomething< / span > < span class = "token operator" > :< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > type< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "Handling "< / span > < span class = "token operator" > +< / span > type < span class = "token operator" > +< / span > < span class = "token string" > " for "< / span > < span class = "token operator" > +< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > id< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "call-apply-bind-与-es6" > < a href = "#call-apply-bind-与-es6" class = "headerlink" title = "call, apply, bind 与 es6" > < / a > call, apply, bind 与 es6< / h1 > < p > js 的函数继承于< code > Function.prototype< / code > 对象，因此每个函数都会有 apply、call、bind 方法< / p >
< blockquote >
< p > call 和 apply 的作用，完全一样，唯一的区别就是在参数上面。< / p >
< / blockquote >
< p > < code > call, apply, bind< / code > 改变函数中 < code > this 指向< / code > 的三兄弟，把< code > this< / code > 绑定到第一个参数对象上< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > displayHobbies< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > < span class = "token operator" > ...< / span > hobbies< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > name< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > likes < / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > hobbies< span class = "token punctuation" > .< / span > < span class = "token function" > join< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > ", "< / span > < span class = "token punctuation" > )< / span > < span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > .< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // 下面两个等价< / span >
< span class = "token function" > displayHobbies< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > call< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Bob"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "swimming"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "basketball"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "anime"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // Bob likes swimming, basketball, anime.< / span >
< span class = "token function" > displayHobbies< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > apply< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Bob"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "swimming"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "basketball"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "anime"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // Bob likes swimming, basketball, anime.< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > < code > bind< / code > 返回的是一个函数，需要手动执行< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > var< / span > p1 < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "张三"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > age< / span > < span class = "token operator" > :< / span > < span class = "token number" > 12< / span > < span class = "token punctuation" > ,< / span >
< span class = "token function-variable function" > func< / span > < span class = "token operator" > :< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > 姓名:< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > name< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > ,年龄:< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > age< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > var< / span > p2 < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "李四"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > age< / span > < span class = "token operator" > :< / span > < span class = "token number" > 15< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
p1< span class = "token punctuation" > .< / span > < span class = "token function" > func< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > bind< / span > < span class = "token punctuation" > (< / span > p2< span class = "token punctuation" > )< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > //姓名:李四,年龄:15< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "for-循环优化" > < a href = "#for-循环优化" class = "headerlink" title = "for 循环优化" > < / a > for 循环优化< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // 每次都要计算array.length< / span >
< span class = "token keyword" > for< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > let< / span > i < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span > i < span class = "token operator" > < < / span > array< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span > i< span class = "token operator" > ++< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > i< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // 使用leng缓存array长度< / span >
< span class = "token keyword" > for< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > let< / span > i < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ,< / span > length < span class = "token operator" > =< / span > array< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span > i < span class = "token operator" > < < / span > length< span class = "token punctuation" > ;< / span > i< span class = "token operator" > ++< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > i< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "数组" > < a href = "#数组" class = "headerlink" title = "数组" > < / a > 数组< / h1 > < h2 id = "扁平化去重升序排列" > < a href = "#扁平化去重升序排列" class = "headerlink" title = "扁平化去重升序排列" > < / a > 扁平化去重升序排列< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > arr < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 3< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 5< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 5< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 6< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 7< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 8< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 9< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 11< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 12< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 12< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 13< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 14< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 10< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
arr< span class = "token punctuation" > .< / span > < span class = "token function" > flat< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > Infinity< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // [1, 2, 2, 3, 4, 5, 5, 6, 7, 8, 9, 11, 12, 12, 13, 14, 10]< / span >
< span class = "token keyword" > let< / span > result < span class = "token operator" > =< / span > Array< span class = "token punctuation" > .< / span > < span class = "token function" > from< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Set< / span > < span class = "token punctuation" > (< / span > arr< span class = "token punctuation" > .< / span > < span class = "token function" > flat< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > Infinity< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > sort< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > a< span class = "token punctuation" > ,< / span > b< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > a < span class = "token operator" > -< / span > b< span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "前端页面埋点-1x1-gif" > < a href = "#前端页面埋点-1x1-gif" class = "headerlink" title = "前端页面埋点 - 1x1.gif" > < / a > 前端页面埋点 - 1x1.gif< / h1 > < p > 通常用在，统计页面点击，曝光，停留时间，签发……等场景< / p >
< ul >
< li > 比 PNG/ JPG 体积小< / li >
< li > 天然跨域< / li >
< / ul >
< pre class = "line-numbers language-markup" data-language = "markup" > < code class = "language-markup" > < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > button< / span > < span class = "token special-attr" > < span class = "token attr-name" > onClick< / span > < span class = "token attr-value" > < span class = "token punctuation attr-equals" > =< / span > < span class = "token punctuation" > "< / span > < span class = "token value javascript language-javascript" > < span class = "token function" > countClick< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < / span > < span class = "token punctuation" > "< / span > < / span > < / span > < span class = "token punctuation" > >< / span > < / span > haorooms< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > button< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > script< / span > < span class = "token punctuation" > >< / span > < / span > < span class = "token script" > < span class = "token language-javascript" >
< span class = "token keyword" > function< / span > < span class = "token function" > countClick< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > new< / span > < span class = "token class-name" > Image< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > src < span class = "token operator" > =< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > ./haorooms.gif?< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > key< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > =< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > value< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > & < / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > Math< span class = "token punctuation" > .< / span > < span class = "token function" > random< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > < / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< / span > < / span > < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > script< / span > < span class = "token punctuation" > >< / span > < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "事件委托" > < a href = "#事件委托" class = "headerlink" title = "事件委托" > < / a > 事件委托< / h1 > < p > 利用冒泡原理，委托父元素执行< / p >
< pre class = "line-numbers language-markup" data-language = "markup" > < code class = "language-markup" > < span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > ul< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > li< / span > < span class = "token punctuation" > >< / span > < / span > 苹果< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > li< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > li< / span > < span class = "token punctuation" > >< / span > < / span > 香蕉< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > li< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < < / span > li< / span > < span class = "token punctuation" > >< / span > < / span > 凤梨< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > li< / span > < span class = "token punctuation" > >< / span > < / span >
< span class = "token tag" > < span class = "token tag" > < span class = "token punctuation" > < /< / span > ul< / span > < span class = "token punctuation" > >< / span > < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > document< span class = "token punctuation" > .< / span > < span class = "token function" > querySelector< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "ul"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function-variable function" > onclick< / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > event< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > let< / span > target < span class = "token operator" > =< / span > event< span class = "token punctuation" > .< / span > target< span class = "token punctuation" > ;< / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > target< span class = "token punctuation" > .< / span > nodeName < span class = "token operator" > ===< / span > < span class = "token string" > "LI"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > target< span class = "token punctuation" > .< / span > innerHTML< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "构造函数-原型模式" > < a href = "#构造函数-原型模式" class = "headerlink" title = "构造函数 + 原型模式" > < / a > 构造函数 + 原型模式< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > Person< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > name< span class = "token punctuation" > ,< / span > age< span class = "token punctuation" > ,< / span > job< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > name < span class = "token operator" > =< / span > name< span class = "token punctuation" > ;< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > age < span class = "token operator" > =< / span > age< span class = "token punctuation" > ;< / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > job < span class = "token operator" > =< / span > job< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token class-name" > Person< / span > < span class = "token punctuation" > .< / span > prototype< span class = "token punctuation" > .< / span > < span class = "token function-variable function" > say< / span > < span class = "token operator" > =< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > text< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > name< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > say:< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > text< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "剩余参数…args" > < a href = "#剩余参数…args" class = "headerlink" title = "剩余参数…args" > < / a > 剩余参数…args< / h1 > < p > 剩余参数< code > args< / code > 数个数组，< code > ...< / code > 解构符< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > fun1< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > param< span class = "token punctuation" > ,< / span > < span class = "token operator" > ...< / span > args< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > alert< / span > < span class = "token punctuation" > (< / span > args< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "跨页面通信" > < a href = "#跨页面通信" class = "headerlink" title = "跨页面通信" > < / a > 跨页面通信< / h1 > < ul >
< li > cookie< / li >
< li > web worker< / li >
< li > localstorage< / li >
< / ul >
< h1 id = "iframe-跨域通信和不跨域通信" > < a href = "#iframe-跨域通信和不跨域通信" class = "headerlink" title = "iframe 跨域通信和不跨域通信" > < / a > iframe 跨域通信和不跨域通信< / h1 > < h2 id = "不跨域" > < a href = "#不跨域" class = "headerlink" title = "不跨域" > < / a > 不跨域< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // fatherSay是父页面全局方法< / span >
window< span class = "token punctuation" > .< / span > parent< span class = "token punctuation" > .< / span > < span class = "token function" > fatherSay< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 父页面Dom< / span >
window< span class = "token punctuation" > .< / span > parent< span class = "token punctuation" > .< / span > document< span class = "token punctuation" > .< / span > < span class = "token function" > getElementById< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "元素id"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 副业页面获取frameID为`iframe_ID`的子页面的Dom< / span >
window< span class = "token punctuation" > .< / span > frames< span class = "token punctuation" > [< / span > < span class = "token string" > "iframe_ID"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > .< / span > document< span class = "token punctuation" > .< / span > < span class = "token function" > getElementById< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "元素id"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "跨域-postMessage" > < a href = "#跨域-postMessage" class = "headerlink" title = "跨域 postMessage" > < / a > 跨域 postMessage< / h2 > < p > 子页面< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > window< span class = "token punctuation" > .< / span > parent< span class = "token punctuation" > .< / span > < span class = "token function" > postMessage< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "hello"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "http://127.0.0.1:8089"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < / span > < / code > < / pre >
< p > 父页面接受< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > window< span class = "token punctuation" > .< / span > < span class = "token function" > addEventListener< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "message"< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > event< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > alert< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > 123< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "对象类型判断" > < a href = "#对象类型判断" class = "headerlink" title = "对象类型判断" > < / a > 对象类型判断< / h1 > < h2 id = "数组-1" > < a href = "#数组-1" class = "headerlink" title = "数组" > < / a > 数组< / h2 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > arr < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
arr < span class = "token keyword" > instanceof< / span > < span class = "token class-name" > Array< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // true< / span >
Array< span class = "token punctuation" > .< / span > < span class = "token function" > isArray< / span > < span class = "token punctuation" > (< / span > arr< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // true< / span >
< span class = "token class-name" > Object< / span > < span class = "token punctuation" > .< / span > prototype< span class = "token punctuation" > .< / span > < span class = "token function" > toString< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > call< / span > < span class = "token punctuation" > (< / span > arr< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // "[object Array]"< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "js-单线程，如何异步" > < a href = "#js-单线程，如何异步" class = "headerlink" title = "js 单线程，如何异步" > < / a > js 单线程，如何异步< / h1 > < ul >
< li > < p > 主线程 执行 js 中所有的代码。< / p >
< / li >
< li > < p > 主线程 在执行过程中发现了需要异步的任务任务后扔给浏览器（浏览器创建多个线程执行，顺便创造一个< code > 回调队列< / code > 。< / p >
< / li >
< li > < p > 主线程 已经执行完毕所有同步代码。监听< code > 回调队列< / code > 一旦 浏览器 中某个线程任务完成将会改变回调函数的状态。主线程查看到某个函数的状态为已完成，就会执行该< code > 回调队列< / code > 中对应的回调函数。< / p >
< / li >
< / ul >
< h1 id = "移动端最小触控区域" > < a href = "#移动端最小触控区域" class = "headerlink" title = "移动端最小触控区域" > < / a > 移动端最小触控区域< / h1 > < p > 苹果推荐是 44pt x 44pt 「具体看 WWDC 14」,通过< code > padding< / code > 、< code > margin< / code > 、< code > height< / code > 等方式进行点击区域扩展< / p >
< h1 id = "js-精度问题" > < a href = "#js-精度问题" class = "headerlink" title = "js 精度问题" > < / a > js 精度问题< / h1 > < p > 常用类库：< code > Math.js< / code > 、< code > Big.js< / code > 、< code > decimal.js< / code > < / p >
< h1 id = "冻结-Object-freeze" > < a href = "#冻结-Object-freeze" class = "headerlink" title = "冻结 Object. freeze()" > < / a > 冻结 Object. freeze()< / h1 > < p > < code > const< / code > 生命的简单变量不可修改，但是复杂对象可以被修改，< code > Object. freeze()< / code > ：可以冻结对象< / p >
< ul >
< li > 不能添加新属性< / li >
< li > 不能删除已有属性< / li >
< li > 不能修改已有属性的可枚举性、可配置性、可写性< / li >
< li > 不能修改已有属性的值< / li >
< li > 不能修改原型< / li >
< / ul >
< p > 浅冻结< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > const< / span > obj1 < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > internal< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
Object< span class = "token punctuation" > .< / span > < span class = "token function" > freeze< / span > < span class = "token punctuation" > (< / span > obj1< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
obj1< span class = "token punctuation" > .< / span > internal< span class = "token punctuation" > .< / span > a < span class = "token operator" > =< / span > < span class = "token string" > "aValue"< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > obj1< span class = "token punctuation" > .< / span > internal< span class = "token punctuation" > .< / span > a< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // aValue< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 递归冻结< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > deepFreeze< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > obj< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // 获取定义在obj上的属性名< / span >
< span class = "token keyword" > var< / span > propNames < span class = "token operator" > =< / span > Object< span class = "token punctuation" > .< / span > < span class = "token function" > getOwnPropertyNames< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 在冻结自身之前冻结属性< / span >
propNames< span class = "token punctuation" > .< / span > < span class = "token function" > forEach< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > name< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > var< / span > prop < span class = "token operator" > =< / span > obj< span class = "token punctuation" > [< / span > name< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 如果prop是个对象， < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > typeof< / span > prop < span class = "token operator" > ==< / span > < span class = "token string" > "object"< / span > < span class = "token operator" > & & < / span > prop < span class = "token operator" > !==< / span > < span class = "token keyword" > null< / span > < span class = "token punctuation" > )< / span > < span class = "token function" > deepFreeze< / span > < span class = "token punctuation" > (< / span > prop< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > Object< span class = "token punctuation" > .< / span > < span class = "token function" > freeze< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "Reflect" > < a href = "#Reflect" class = "headerlink" title = "Reflect" > < / a > Reflect< / h1 > < h2 id = "Reflect-get-target-propertyKey-value-receiver" > < a href = "#Reflect-get-target-propertyKey-value-receiver" class = "headerlink" title = "Reflect.get(target, propertyKey, value[receiver])" > < / a > Reflect.get(target, propertyKey, value[receiver])< / h2 > < p > 获取对象身上某个属性的值，类似于 target[name]。< / p >
< h2 id = "Reflect-set-target-propertyKey-value-receiver" > < a href = "#Reflect-set-target-propertyKey-value-receiver" class = "headerlink" title = "Reflect.set(target, propertyKey, value[receiver])" > < / a > Reflect.set(target, propertyKey, value[receiver])< / h2 > < p > 将值分配给属性的函数。返回一个 Boolean， ， < / p >
< h2 id = "Reflect-has-target-propertyKey" > < a href = "#Reflect-has-target-propertyKey" class = "headerlink" title = "Reflect.has(target, propertyKey)" > < / a > Reflect.has(target, propertyKey)< / h2 > < p > 判断一个对象是否存在某个属性，和 in 运算符 的功能完全相同。< / p >
< h1 id = "if-else-优化" > < a href = "#if-else-优化" class = "headerlink" title = "if else 优化" > < / a > if else 优化< / h1 > < h2 id = "表驱动编程" > < a href = "#表驱动编程" class = "headerlink" title = "表驱动编程" > < / a > 表驱动编程< / h2 > < p > 空间换时间，设置< code > obj={ key:value} < / code > ，通过< code > obj[key]< / code > 取值< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token function" > calculateGrade< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > score< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > const< / span > table < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token number" > 100< / span > < span class = "token operator" > :< / span > < span class = "token string" > 'A'< / span > < span class = "token punctuation" > ,< / span >
< span class = "token number" > 90< / span > < span class = "token operator" > :< / span > < span class = "token string" > 'A'< / span > < span class = "token punctuation" > ,< / span >
< span class = "token number" > 80< / span > < span class = "token operator" > :< / span > < span class = "token string" > 'B'< / span > < span class = "token punctuation" > ,< / span >
< span class = "token number" > 70< / span > < span class = "token operator" > :< / span > < span class = "token string" > 'C'< / span > < span class = "token punctuation" > ,< / span >
< span class = "token number" > 60< / span > < span class = "token operator" > :< / span > < span class = "token string" > 'D'< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > others< / span > < span class = "token operator" > :< / span > < span class = "token string" > 'E'< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > table< span class = "token punctuation" > [< / span > Math< span class = "token punctuation" > .< / span > < span class = "token function" > floor< / span > < span class = "token punctuation" > (< / span > score< span class = "token operator" > /< / span > < span class = "token number" > 10< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > *< / span > < span class = "token number" > 10< / span > < span class = "token punctuation" > ]< / span > < span class = "token operator" > ||< / span > table< span class = "token punctuation" > [< / span > < span class = "token string" > 'others'< / span > < span class = "token punctuation" > ]< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "短路运算" > < a href = "#短路运算" class = "headerlink" title = "短路运算" > < / a > 短路运算< / h2 > < p > react 没有< code > v-if< / code > ，运用比较频繁< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > // 函数组件< / span >
< span class = "token keyword" > const< / span > < span class = "token function-variable function" > Home< / span > < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token operator" > < < / span > div< span class = "token operator" > >< / span > home< span class = "token operator" > < < / span > < span class = "token operator" > /< / span > div< span class = "token operator" > >< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > { < / span >
< span class = "token boolean" > true< / span > < span class = "token operator" > & & < / span > < span class = "token operator" > < < / span > Home < span class = "token operator" > /< / span > < span class = "token operator" > >< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "使用有意义且易读的变量名" > < a href = "#使用有意义且易读的变量名" class = "headerlink" title = "使用有意义且易读的变量名" > < / a > 使用有意义且易读的变量名< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎 < span class = "token keyword" > const< / span > yyyymmdstr < span class = "token operator" > =< / span > < span class = "token function" > moment< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > format< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "YYYY/MM/DD"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
👍 < span class = "token keyword" > const< / span > currentDate < span class = "token operator" > =< / span > < span class = "token function" > moment< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > format< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "YYYY/MM/DD"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "使用有意义的变量代替数组下标" > < a href = "#使用有意义的变量代替数组下标" class = "headerlink" title = "使用有意义的变量代替数组下标" > < / a > 使用有意义的变量代替数组下标< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎
< span class = "token keyword" > const< / span > address < span class = "token operator" > =< / span > < span class = "token string" > "One Infinite Loop, Cupertino 95014"< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > const< / span > cityZipCodeRegex < span class = "token operator" > =< / span > < span class = "token regex" > < span class = "token regex-delimiter" > /< / span > < span class = "token regex-source language-regex" > ^[^,\\]+[,\\\s]+(.+?)\s*(\d{ 5} )?$< / span > < span class = "token regex-delimiter" > /< / span > < / span > < span class = "token punctuation" > ;< / span >
< span class = "token function" > saveCityZipCode< / span > < span class = "token punctuation" > (< / span >
address< span class = "token punctuation" > .< / span > < span class = "token function" > match< / span > < span class = "token punctuation" > (< / span > cityZipCodeRegex< span class = "token punctuation" > )< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span >
address< span class = "token punctuation" > .< / span > < span class = "token function" > match< / span > < span class = "token punctuation" > (< / span > cityZipCodeRegex< span class = "token punctuation" > )< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > ]< / span >
< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
👍
< span class = "token keyword" > const< / span > address < span class = "token operator" > =< / span > < span class = "token string" > "One Infinite Loop, Cupertino 95014"< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > const< / span > cityZipCodeRegex < span class = "token operator" > =< / span > < span class = "token regex" > < span class = "token regex-delimiter" > /< / span > < span class = "token regex-source language-regex" > ^[^,\\]+[,\\\s]+(.+?)\s*(\d{ 5} )?$< / span > < span class = "token regex-delimiter" > /< / span > < / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > const< / span > < span class = "token punctuation" > [< / span > _< span class = "token punctuation" > ,< / span > city< span class = "token punctuation" > ,< / span > zipCode< span class = "token punctuation" > ]< / span > < span class = "token operator" > =< / span > address< span class = "token punctuation" > .< / span > < span class = "token function" > match< / span > < span class = "token punctuation" > (< / span > cityZipCodeRegex< span class = "token punctuation" > )< / span > < span class = "token operator" > ||< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token function" > saveCityZipCode< / span > < span class = "token punctuation" > (< / span > city< span class = "token punctuation" > ,< / span > zipCode< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "变量名要简洁" > < a href = "#变量名要简洁" class = "headerlink" title = "变量名要简洁" > < / a > 变量名要简洁< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎
< span class = "token keyword" > const< / span > Car < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > carMake< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Honda"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > carModel< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Accord"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > carColor< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Blue"< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > paintCar< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > car< span class = "token punctuation" > ,< / span > color< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
car< span class = "token punctuation" > .< / span > carColor < span class = "token operator" > =< / span > color< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
👍
< span class = "token keyword" > const< / span > Car < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > make< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Honda"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > model< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Accord"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > color< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Blue"< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > paintCar< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > car< span class = "token punctuation" > ,< / span > color< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
car< span class = "token punctuation" > .< / span > color < span class = "token operator" > =< / span > color< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "消除魔术字符串" > < a href = "#消除魔术字符串" class = "headerlink" title = "消除魔术字符串" > < / a > 消除魔术字符串< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎 < span class = "token function" > setTimeout< / span > < span class = "token punctuation" > (< / span > blastOff< span class = "token punctuation" > ,< / span > < span class = "token number" > 86400000< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
👍 < span class = "token keyword" > const< / span > < span class = "token constant" > MILLISECONDS_PER_DAY< / span > < span class = "token operator" > =< / span > < span class = "token number" > 60< / span > < span class = "token operator" > *< / span > < span class = "token number" > 60< / span > < span class = "token operator" > *< / span > < span class = "token number" > 24< / span > < span class = "token operator" > *< / span > < span class = "token number" > 1000< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > //86400000;< / span >
< span class = "token function" > setTimeout< / span > < span class = "token punctuation" > (< / span > blastOff< span class = "token punctuation" > ,< / span > < span class = "token constant" > MILLISECONDS_PER_DAY< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "使用默认参数替代短路运算符" > < a href = "#使用默认参数替代短路运算符" class = "headerlink" title = "使用默认参数替代短路运算符" > < / a > 使用默认参数替代短路运算符< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎
< span class = "token keyword" > function< / span > < span class = "token function" > createMicrobrewery< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > name< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > const< / span > breweryName < span class = "token operator" > =< / span > name < span class = "token operator" > ||< / span > < span class = "token string" > "Hipster Brew Co."< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // ...< / span >
< span class = "token punctuation" > } < / span >
👍
< span class = "token keyword" > function< / span > < span class = "token function" > createMicrobrewery< / span > < span class = "token punctuation" > (< / span > name < span class = "token operator" > =< / span > < span class = "token string" > "Hipster Brew Co."< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // ...< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "一个函数" > < a href = "#一个函数" class = "headerlink" title = "一个函数" > < / a > 一个函数< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎
< span class = "token keyword" > function< / span > < span class = "token function" > emailClients< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > clients< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
clients< span class = "token punctuation" > .< / span > < span class = "token function" > forEach< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > client< / span > < span class = "token operator" > =>< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > const< / span > clientRecord < span class = "token operator" > =< / span > database< span class = "token punctuation" > .< / span > < span class = "token function" > lookup< / span > < span class = "token punctuation" > (< / span > client< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > clientRecord< span class = "token punctuation" > .< / span > < span class = "token function" > isActive< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > email< / span > < span class = "token punctuation" > (< / span > client< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
👍
< span class = "token keyword" > function< / span > < span class = "token function" > emailActiveClients< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > clients< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
clients< span class = "token punctuation" > .< / span > < span class = "token function" > filter< / span > < span class = "token punctuation" > (< / span > isActiveClient< span class = "token punctuation" > )< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > forEach< / span > < span class = "token punctuation" > (< / span > email< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > function< / span > < span class = "token function" > isActiveClient< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > client< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > const< / span > clientRecord < span class = "token operator" > =< / span > database< span class = "token punctuation" > .< / span > < span class = "token function" > lookup< / span > < span class = "token punctuation" > (< / span > client< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > clientRecord< span class = "token punctuation" > .< / span > < span class = "token function" > isActive< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > -< / span > 分割线< span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > --< / span > < span class = "token operator" > -< / span >
👎
< span class = "token keyword" > function< / span > < span class = "token function" > createFile< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > name< span class = "token punctuation" > ,< / span > temp< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > temp< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
fs< span class = "token punctuation" > .< / span > < span class = "token function" > create< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > ./temp/< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > name< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token keyword" > else< / span > < span class = "token punctuation" > { < / span >
fs< span class = "token punctuation" > .< / span > < span class = "token function" > create< / span > < span class = "token punctuation" > (< / span > name< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span >
👍
< span class = "token keyword" > function< / span > < span class = "token function" > createFile< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > name< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
fs< span class = "token punctuation" > .< / span > < span class = "token function" > create< / span > < span class = "token punctuation" > (< / span > name< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > function< / span > < span class = "token function" > createTempFile< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > name< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > createFile< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > ./temp/< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > name< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "函数参数不多于-2-个，如果有很多参数就利用-object-传递，并使用解构" > < a href = "#函数参数不多于-2-个，如果有很多参数就利用-object-传递，并使用解构" class = "headerlink" title = "函数参数不多于 2 个，如果有很多参数就利用 object 传递，并使用解构" > < / a > 函数参数不多于 2 个，如果有很多参数就利用 object 传递，并使用解构< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎
< span class = "token keyword" > function< / span > < span class = "token function" > createMenu< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > title< span class = "token punctuation" > ,< / span > body< span class = "token punctuation" > ,< / span > buttonText< span class = "token punctuation" > ,< / span > cancellable< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // ...< / span >
< span class = "token punctuation" > } < / span >
< span class = "token function" > createMenu< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "Foo"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "Bar"< / span > < span class = "token punctuation" > ,< / span > < span class = "token string" > "Baz"< / span > < span class = "token punctuation" > ,< / span > < span class = "token boolean" > true< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
👍
< span class = "token keyword" > function< / span > < span class = "token function" > createMenu< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > < span class = "token punctuation" > { < / span > title< span class = "token punctuation" > ,< / span > body< span class = "token punctuation" > ,< / span > buttonText< span class = "token punctuation" > ,< / span > cancellable < span class = "token punctuation" > } < / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // ...< / span >
< span class = "token punctuation" > } < / span >
< span class = "token function" > createMenu< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > title< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Foo"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > body< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Bar"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > buttonText< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Baz"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > cancellable< / span > < span class = "token operator" > :< / span > < span class = "token boolean" > true< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "函数名应该直接反映函数的作用" > < a href = "#函数名应该直接反映函数的作用" class = "headerlink" title = "函数名应该直接反映函数的作用" > < / a > 函数名应该直接反映函数的作用< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎
< span class = "token keyword" > function< / span > < span class = "token function" > addToDate< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > date< span class = "token punctuation" > ,< / span > month< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // ...< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > const< / span > date < span class = "token operator" > =< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Date< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // It's hard to tell from the function name what is added< / span >
< span class = "token function" > addToDate< / span > < span class = "token punctuation" > (< / span > date< span class = "token punctuation" > ,< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
👍
< span class = "token keyword" > function< / span > < span class = "token function" > addMonthToDate< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > month< span class = "token punctuation" > ,< / span > date< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // ...< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > const< / span > date < span class = "token operator" > =< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Date< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token function" > addMonthToDate< / span > < span class = "token punctuation" > (< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ,< / span > date< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "尽量使用纯函数" > < a href = "#尽量使用纯函数" class = "headerlink" title = "尽量使用纯函数" > < / a > 尽量使用纯函数< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎
< span class = "token keyword" > const< / span > programmerOutput < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span >
< span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Uncle Bobby"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > linesOfCode< / span > < span class = "token operator" > :< / span > < span class = "token number" > 500< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Suzie Q"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > linesOfCode< / span > < span class = "token operator" > :< / span > < span class = "token number" > 1500< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Jimmy Gosling"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > linesOfCode< / span > < span class = "token operator" > :< / span > < span class = "token number" > 150< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Gracie Hopper"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > linesOfCode< / span > < span class = "token operator" > :< / span > < span class = "token number" > 1000< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > totalOutput < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > for< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > let< / span > i < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span > i < span class = "token operator" > < < / span > programmerOutput< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span > i< span class = "token operator" > ++< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
totalOutput < span class = "token operator" > +=< / span > programmerOutput< span class = "token punctuation" > [< / span > i< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > .< / span > linesOfCode< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
👍
< span class = "token keyword" > const< / span > programmerOutput < span class = "token operator" > =< / span > < span class = "token punctuation" > [< / span >
< span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Uncle Bobby"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > linesOfCode< / span > < span class = "token operator" > :< / span > < span class = "token number" > 500< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Suzie Q"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > linesOfCode< / span > < span class = "token operator" > :< / span > < span class = "token number" > 1500< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Jimmy Gosling"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > linesOfCode< / span > < span class = "token operator" > :< / span > < span class = "token number" > 150< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > name< / span > < span class = "token operator" > :< / span > < span class = "token string" > "Gracie Hopper"< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > linesOfCode< / span > < span class = "token operator" > :< / span > < span class = "token number" > 1000< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > const< / span > totalOutput < span class = "token operator" > =< / span > programmerOutput< span class = "token punctuation" > .< / span > < span class = "token function" > reduce< / span > < span class = "token punctuation" > (< / span >
< span class = "token punctuation" > (< / span > < span class = "token parameter" > totalLines< span class = "token punctuation" > ,< / span > output< / span > < span class = "token punctuation" > )< / span > < span class = "token operator" > =>< / span > totalLines < span class = "token operator" > +< / span > output< span class = "token punctuation" > .< / span > linesOfCode< span class = "token punctuation" > ,< / span >
< span class = "token number" > 0< / span >
< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "不要过度优化" > < a href = "#不要过度优化" class = "headerlink" title = "不要过度优化" > < / a > 不要过度优化< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > 👎
< span class = "token comment" > // 现代浏览器对于迭代器做了内部优化< / span >
< span class = "token keyword" > for< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > let< / span > i < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ,< / span > len < span class = "token operator" > =< / span > list< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span > i < span class = "token operator" > < < / span > len< span class = "token punctuation" > ;< / span > i< span class = "token operator" > ++< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // ...< / span >
< span class = "token punctuation" > } < / span >
👍
< span class = "token keyword" > for< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > let< / span > i < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span > i < span class = "token operator" > < < / span > list< span class = "token punctuation" > .< / span > length< span class = "token punctuation" > ;< / span > i< span class = "token operator" > ++< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // ...< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "关于模块化" > < a href = "#关于模块化" class = "headerlink" title = "关于模块化" > < / a > 关于模块化< / h1 > < h2 id = "无模块化" > < a href = "#无模块化" class = "headerlink" title = "无模块化" > < / a > 无模块化< / h2 > < blockquote >
< p > 污染全局作用域、维护成本高、依赖关系不明显< / p >
< / blockquote >
< p > script 标签引入 js 文件，相互罗列，但是被依赖的放在前面，否则使用就会报错。如下：< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token operator" > < < / span > script src< span class = "token operator" > =< / span > < span class = "token string" > "jquery.js"< / span > < span class = "token operator" > >< / span > < span class = "token operator" > < < / span > < span class = "token operator" > /< / span > script< span class = "token operator" > >< / span >
< span class = "token operator" > < < / span > script src< span class = "token operator" > =< / span > < span class = "token string" > "main.js"< / span > < span class = "token operator" > >< / span > < span class = "token operator" > < < / span > < span class = "token operator" > /< / span > script< span class = "token operator" > >< / span >
< span class = "token operator" > < < / span > script src< span class = "token operator" > =< / span > < span class = "token string" > "other1.js"< / span > < span class = "token operator" > >< / span > < span class = "token operator" > < < / span > < span class = "token operator" > /< / span > script< span class = "token operator" > >< / span >
< span class = "token operator" > < < / span > script src< span class = "token operator" > =< / span > < span class = "token string" > "other2.js"< / span > < span class = "token operator" > >< / span > < span class = "token operator" > < < / span > < span class = "token operator" > /< / span > script< span class = "token operator" > >< / span >
< span class = "token operator" > < < / span > script src< span class = "token operator" > =< / span > < span class = "token string" > "other3.js"< / span > < span class = "token operator" > >< / span > < span class = "token operator" > < < / span > < span class = "token operator" > /< / span > script< span class = "token operator" > >< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "CommonJS-规范-同步" > < a href = "#CommonJS-规范-同步" class = "headerlink" title = "CommonJS 规范(同步)" > < / a > CommonJS 规范(同步)< / h2 > < p > 该规范最初是用在服务器端的 node 的， ： ， ） ， < / p >
< blockquote >
< p > module.exports 本身就是一个对象< / p >
< / blockquote >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > module< span class = "token punctuation" > .< / span > exports < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > foo< / span > < span class = "token operator" > :< / span > < span class = "token string" > "bar"< / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > //true< / span >
module< span class = "token punctuation" > .< / span > exports< span class = "token punctuation" > .< / span > foo < span class = "token operator" > =< / span > < span class = "token string" > "bar"< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > //true。< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > CommonJS 用同步的方式加载模块。在服务端， ， ， ， ， < / p >
< h2 id = "AMD-规范-RequireJS" > < a href = "#AMD-规范-RequireJS" class = "headerlink" title = "AMD 规范(RequireJS)" > < / a > AMD 规范(RequireJS)< / h2 > < p > 承接上文， ， ， < / p >
< ul >
< li > < code > require([module], callback)< / code > ：加载模块< / li >
< li > < code > define(id, [depends], callback)< / code > ：定义模块< / li >
< li > < code > require.config()< / code > ：配置路径、依赖关系< / li >
< / ul >
< h2 id = "CMD-规范-SeaJS" > < a href = "#CMD-规范-SeaJS" class = "headerlink" title = "CMD 规范(SeaJS)" > < / a > CMD 规范(SeaJS)< / h2 > < p > CMD 是 在推广过程中对模块定义的规范化产出< / p >
< h2 id = "ES6-import-x2F-export" > < a href = "#ES6-import-x2F-export" class = "headerlink" title = "ES6 import/export" > < / a > ES6 import/ export< / h2 > < p > 通过 babel 将不被支持的 import 编译为当前受到广泛支持的 AMD 规范< / p >
< h1 id = "AMD模块化实现" > < a href = "#AMD模块化实现" class = "headerlink" title = "AMD模块化实现" > < / a > AMD模块化实现< / h1 > < h2 id = "define-函数" > < a href = "#define-函数" class = "headerlink" title = "define 函数" > < / a > define 函数< / h2 > < p > 用来声明模块名< code > module< / code > ，依赖数组< code > deps< / code > ，以及模块的作用< code > callback< / code > < / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > var< / span > module < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > var< / span > stack < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > //模块存储栈，存的是模块执行后的结果< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > define< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > module< span class = "token punctuation" > ,< / span > deps< span class = "token punctuation" > ,< / span > callback< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
stack< span class = "token punctuation" > [< / span > module< span class = "token punctuation" > ]< / span > < span class = "token operator" > =< / span > < span class = "token function" > callback< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > apply< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > null< / span > < span class = "token punctuation" > ,< / span > deps< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 压栈< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > stack< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 查看栈存储的模块< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > define< / span > < span class = "token operator" > :< / span > define < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 调用< code > define< / code > 试试，发现 < code > calc< / code > 模块被压入了< code > stack 模块栈中< / code > < / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > module< span class = "token punctuation" > .< / span > < span class = "token function" > define< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "calc"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token punctuation" > { < / span >
< span class = "token function-variable function" > first< / span > < span class = "token operator" > :< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > arr< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > arr< span class = "token punctuation" > [< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // { calc: { first: ƒ } } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h2 id = "deps-依赖-导入" > < a href = "#deps-依赖-导入" class = "headerlink" title = "deps 依赖(导入)" > < / a > deps 依赖(导入)< / h2 > < p > 对上面的 < code > define< / code > 函数稍加改造，这一步过程的本质，就是对 deps< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > var< / span > module < span class = "token operator" > =< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > window< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > var< / span > stack < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > //模块存储栈，< / span >
< span class = "token keyword" > function< / span > < span class = "token function" > define< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > module< span class = "token punctuation" > ,< / span > deps< span class = "token punctuation" > ,< / span > callback< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token comment" > // 把 define 函数依赖数组中的模块从 stack 模块中拿出< / span >
deps< span class = "token punctuation" > .< / span > < span class = "token function" > map< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > mod< span class = "token punctuation" > ,< / span > index< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
deps< span class = "token punctuation" > [< / span > index< span class = "token punctuation" > ]< / span > < span class = "token operator" > =< / span > stack< span class = "token punctuation" > [< / span > mod< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 赋值给当前模块的 deps< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
stack< span class = "token punctuation" > [< / span > module< span class = "token punctuation" > ]< / span > < span class = "token operator" > =< / span > < span class = "token function" > callback< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > apply< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > null< / span > < span class = "token punctuation" > ,< / span > deps< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > stack< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 查看栈存储的模块< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > define< / span > < span class = "token operator" > :< / span > define < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > (< / span > window< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
module< span class = "token punctuation" > .< / span > < span class = "token function" > define< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "calc"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token punctuation" > { < / span >
< span class = "token function-variable function" > first< / span > < span class = "token operator" > :< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > arr< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > arr< span class = "token punctuation" > [< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
module< span class = "token punctuation" > .< / span > < span class = "token function" > define< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "number"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "calc"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > calc< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > res< / span > < span class = "token operator" > :< / span > calc< span class = "token punctuation" > .< / span > < span class = "token function" > first< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > [< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 3< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ,< / span > < span class = "token comment" > //4< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token comment" > // 此时 stack 打印的结果为< / span >
< span class = "token comment" > //> calc: { first: ƒ} < / span >
< span class = "token comment" > //> number: { res: 4} < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< blockquote >
< p > 从本质上看， < code > return { } < / code > ，也就相当于 export 导出< / p >
< / blockquote >
< h2 id = "老生常谈的指针" > < a href = "#老生常谈的指针" class = "headerlink" title = "老生常谈的指针" > < / a > 老生常谈的指针< / h2 > < p > 说到底，< code > stack< / code > 中 < code > a模块< / code > export 是一个指针，< code > { a:value} < / code > (内存地址)，所以，< code > b 模块< / code > 会改变< code > a.a< / code > 的值，这点和 < code > cmd< / code > 不同< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > module< span class = "token punctuation" > .< / span > < span class = "token function" > define< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "a"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > a< / span > < span class = "token operator" > :< / span > < span class = "token number" > 1< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
module< span class = "token punctuation" > .< / span > < span class = "token function" > define< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "b"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "a"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > a< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
a< span class = "token punctuation" > .< / span > a < span class = "token operator" > =< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
module< span class = "token punctuation" > .< / span > < span class = "token function" > define< / span > < span class = "token punctuation" > (< / span > < span class = "token string" > "c"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > [< / span > < span class = "token string" > "a"< / span > < span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > function< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > a< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > a< span class = "token punctuation" > .< / span > a< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 2< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "缘起-Object-defineProperty" > < a href = "#缘起-Object-defineProperty" class = "headerlink" title = "缘起 Object.defineProperty()" > < / a > 缘起 Object.defineProperty()< / h1 > < p > 给< code > 目标对象< / code > 上定义一个新属性，或者修改< code > 目标对象< / code > 属性，并且返回新对象< / p >
< h1 id = "上帝的钥匙-get-amp-set" > < a href = "#上帝的钥匙-get-amp-set" class = "headerlink" title = "上帝的钥匙 get & set" > < / a > 上帝的钥匙 get & set< / h1 > < p > 属性的< code > getter< / code > 函数，如果没有 < code > getter< / code > 则尾 < code > undefined< / code > 。当访问该属性时，会调用此函数.< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > obj < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
Object< span class = "token punctuation" > .< / span > < span class = "token function" > defineProperty< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > ,< / span > < span class = "token string" > "a"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > get< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > < span class = "token number" > 7< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token function" > set< / span > < span class = "token punctuation" > (< / span > val< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > FAILED！ < / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > val< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > ，但是被重写 set 劫持了< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > .< / span > a< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
obj< span class = "token punctuation" > .< / span > a < span class = "token operator" > =< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< blockquote >
< p > 上帝的钥匙被找到了< / p >
< / blockquote >
< p > 劫持！劫持！还是 TMD 劫持！< / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > obj < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > tempValue < span class = "token operator" > =< / span > < span class = "token number" > 0< / span > < span class = "token punctuation" > ;< / span >
Object< span class = "token punctuation" > .< / span > < span class = "token function" > defineProperty< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > ,< / span > < span class = "token string" > "a"< / span > < span class = "token punctuation" > ,< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > get< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > return< / span > tempValue< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token function" > set< / span > < span class = "token punctuation" > (< / span > newValue< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
tempValue < span class = "token operator" > =< / span > newValue< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > .< / span > a< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 0< / span >
obj< span class = "token punctuation" > .< / span > a < span class = "token operator" > =< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > .< / span > a< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 4< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "封装-defineReactive-obj-prop-val" > < a href = "#封装-defineReactive-obj-prop-val" class = "headerlink" title = "封装 defineReactive(obj, prop, val)" > < / a > 封装 defineReactive(obj, prop, val)< / h1 > < blockquote >
< p > 这里 defineReactive 第三个参数 val 替代了上一步中全局变量< code > tempValue< / code > ，对于 get()、set()来说，访问到了其他函数内部的变量，所以形成了闭包< / p >
< / blockquote >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > function< / span > < span class = "token function" > defineReactive< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > obj< span class = "token punctuation" > ,< / span > prop< span class = "token punctuation" > ,< / span > val< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
Object< span class = "token punctuation" > .< / span > < span class = "token function" > defineProperty< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > ,< / span > prop< span class = "token punctuation" > ,< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > get< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > 劫持，你访问了< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > prop< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > 属性< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > val< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token function" > set< / span > < span class = "token punctuation" > (< / span > newValue< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > val < span class = "token operator" > ===< / span > newValue< span class = "token punctuation" > )< / span > < span class = "token keyword" > return< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > 劫持，你改变了< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > prop< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > 属性< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
val < span class = "token operator" > =< / span > newValue< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > let< / span > obj < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token function" > defineReactive< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > ,< / span > < span class = "token string" > "a"< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > .< / span > a< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 劫持， < / span >
obj< span class = "token punctuation" > .< / span > a < span class = "token operator" > =< / span > < span class = "token number" > 7< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 劫持， < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > .< / span > a< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 劫持， < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< h1 id = "递归侦测" > < a href = "#递归侦测" class = "headerlink" title = "递归侦测" > < / a > 递归侦测< / h1 > < pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > obj < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > a< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > b< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > { < / span > < span class = "token literal-property property" > c< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > { < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span >
< span class = "token function" > defineReactive< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > ,< / span > < span class = "token string" > "a"< / span > < span class = "token punctuation" > ,< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< blockquote >
2023-11-07 16:12:40 +08:00
< p > 如何自动让< code > obj< / code > 对象的全部属性都< code > reactive< / code > 呢？< / p >
2023-11-06 16:05:27 +08:00
< / blockquote >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > let< / span > obj < span class = "token operator" > =< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > a< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > b< / span > < span class = "token operator" > :< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > c< / span > < span class = "token operator" > :< / span > < span class = "token number" > 5< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > d< / span > < span class = "token operator" > :< / span > < span class = "token number" > 4< / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ;< / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > 定义个方法< code > observe< / code > ，递归 < code > obj< / code > 的每一层的每个 < code > prop< / code > ，检测是否有< code > __ob__< / code > ，如果没有，< code > defineReactive< / code > ，并且挂一个< code > Observer< / code > 实例在这个< code > props< / code > 上，例如：< / p >
< p > < code > Observer对象< / code > < / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > class< / span > < span class = "token class-name" > Observer< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > constructor< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > value< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > def< / span > < span class = "token punctuation" > (< / span > value< span class = "token punctuation" > ,< / span > < span class = "token string" > "__ob__"< / span > < span class = "token punctuation" > ,< / span > < span class = "token keyword" > this< / span > < span class = "token punctuation" > ,< / span > < span class = "token boolean" > false< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 不可枚举， < / span >
< span class = "token keyword" > this< / span > < span class = "token punctuation" > .< / span > < span class = "token function" > walk< / span > < span class = "token punctuation" > (< / span > value< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token comment" > // 遍历每一个 prop的 value< / span >
< span class = "token function" > walk< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > value< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > for< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > let< / span > prop < span class = "token keyword" > in< / span > value< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token function" > defineReactive< / span > < span class = "token punctuation" > (< / span > value< span class = "token punctuation" > ,< / span > prop< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > < code > defineReactive.js< / code > < / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token keyword" > export< / span > < span class = "token keyword" > default< / span > < span class = "token keyword" > function< / span > < span class = "token function" > defineReactive< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > obj< span class = "token punctuation" > ,< / span > prop< span class = "token punctuation" > ,< / span > val< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > arguments< span class = "token punctuation" > .< / span > length < span class = "token operator" > ===< / span > < span class = "token number" > 2< / span > < span class = "token punctuation" > )< / span > val < span class = "token operator" > =< / span > obj< span class = "token punctuation" > [< / span > prop< span class = "token punctuation" > ]< / span > < span class = "token punctuation" > ;< / span > < span class = "token comment" > // 如果2个参数< / span >
< span class = "token keyword" > let< / span > childNode < span class = "token operator" > =< / span > < span class = "token function" > observe< / span > < span class = "token punctuation" > (< / span > val< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
Object< span class = "token punctuation" > .< / span > < span class = "token function" > defineProperty< / span > < span class = "token punctuation" > (< / span > obj< span class = "token punctuation" > ,< / span > prop< span class = "token punctuation" > ,< / span > < span class = "token punctuation" > { < / span >
< span class = "token literal-property property" > enumerable< / span > < span class = "token operator" > :< / span > < span class = "token boolean" > true< / span > < span class = "token punctuation" > ,< / span >
< span class = "token literal-property property" > configurable< / span > < span class = "token operator" > :< / span > < span class = "token boolean" > true< / span > < span class = "token punctuation" > ,< / span >
< span class = "token function" > get< / span > < span class = "token punctuation" > (< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > 你访问了< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > prop< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > 属性< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > return< / span > val< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token function" > set< / span > < span class = "token punctuation" > (< / span > newValue< span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > val < span class = "token operator" > ===< / span > newValue< span class = "token punctuation" > )< / span > < span class = "token keyword" > return< / span > < span class = "token punctuation" > ;< / span >
console< span class = "token punctuation" > .< / span > < span class = "token function" > log< / span > < span class = "token punctuation" > (< / span > < span class = "token template-string" > < span class = "token template-punctuation string" > `< / span > < span class = "token string" > 你改变了< / span > < span class = "token interpolation" > < span class = "token interpolation-punctuation punctuation" > ${ < / span > prop< span class = "token interpolation-punctuation punctuation" > } < / span > < / span > < span class = "token string" > 属性< / span > < span class = "token template-punctuation string" > `< / span > < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
val < span class = "token operator" > =< / span > newValue< span class = "token punctuation" > ;< / span >
childNode < span class = "token operator" > =< / span > < span class = "token function" > observe< / span > < span class = "token punctuation" > (< / span > newValue< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > ,< / span >
< span class = "token punctuation" > } < / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
< p > < code > observe.js< / code > < / p >
< pre class = "line-numbers language-javascript" data-language = "javascript" > < code class = "language-javascript" > < span class = "token comment" > /**
* 检测 obj 身上有没有 __ob__(Observer 实例)
* @param { *} value
* @returns
*/< / span >
< span class = "token keyword" > export< / span > < span class = "token keyword" > default< / span > < span class = "token keyword" > function< / span > < span class = "token function" > observe< / span > < span class = "token punctuation" > (< / span > < span class = "token parameter" > value< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > typeof< / span > value < span class = "token operator" > !=< / span > < span class = "token string" > "object"< / span > < span class = "token punctuation" > )< / span > < span class = "token keyword" > return< / span > < span class = "token punctuation" > ;< / span >
< span class = "token keyword" > let< / span > ob< span class = "token punctuation" > ;< / span >
< span class = "token comment" > //! 用__ob__是为了属性不重名， < / span >
< span class = "token keyword" > if< / span > < span class = "token punctuation" > (< / span > < span class = "token keyword" > typeof< / span > value< span class = "token punctuation" > .< / span > __ob__ < span class = "token operator" > !=< / span > < span class = "token string" > "undefined"< / span > < span class = "token punctuation" > )< / span > < span class = "token punctuation" > { < / span >
ob < span class = "token operator" > =< / span > value< span class = "token punctuation" > .< / span > __ob__< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span class = "token keyword" > else< / span > < span class = "token punctuation" > { < / span >
ob < span class = "token operator" > =< / span > < span class = "token keyword" > new< / span > < span class = "token class-name" > Observer< / span > < span class = "token punctuation" > (< / span > value< span class = "token punctuation" > )< / span > < span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span >
< span class = "token keyword" > return< / span > ob< span class = "token punctuation" > ;< / span >
< span class = "token punctuation" > } < / span > < span aria-hidden = "true" class = "line-numbers-rows" > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < span > < / span > < / span > < / code > < / pre >
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