576 lines
9.8 KiB
Markdown
576 lines
9.8 KiB
Markdown
---
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title: css奇技淫巧
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categories:
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- CS
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status: doing
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abbrlink: 20942
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---
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# grid 布局
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> flex 布局操纵的是一维、一行/一列，grid 布局具备操纵二维的能力
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设为网格布局以后，容器子元素（项目）的`float`、`display: inline-block`、`display: table-cell`、`vertical-align`和 `column-`等设置都将失效。
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- grid-template-columns: 定义每一列的列宽
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- grid-template-rows: 定义每一行的行高
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- grid-row-gap: 行间距
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- grid-column-gap: 列间距
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- grid-gap: 行列间距合并
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- grid-template-areas: 一个区域由单个或多个单元格组成
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- grid-auto-flow: 默认值是 row，即"先行后列",即先填满第一行，再开始放入第二行
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- justify-items: `单元格内容`的水平对齐
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- align-items: `单元格内容`垂直对齐
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- place-items: align-items 属性和 justify-items 属性的合并简写形式
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- justify-content: `整个内容区域`水平对齐
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- align-content: `整个内容区域`垂直对齐
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- place-content: align-content 属性和 justify-content 属性的合并简写形式
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> 设置的行或者列比较多的时候，可以使用 repeat()这个函数简化重复的值
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## repeat()
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第一个参数是重复的次数，第二个参数是所要重复的值、也可以是某个模式
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```css
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/* 重复 3个100px的列 */
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grid-template-columns: repeat(3, 100px);
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/* 重复这种布局2次 */
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grid-template-columns: repeat(2, 100px 20px 80px);
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/* 自动填充，直到容器放不下为止 */
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grid-template-columns: repeat(auto-fill, 100px);
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```
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## fr
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方便表示比例关系，网格布局提供了 fr 关键字
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```css
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grid-template-columns: 1fr 1fr;
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```
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## grid-template-areas
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```css
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grid-template-areas:
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"header header header"
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"main main sidebar"
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"footer footer footer";
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```
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## item 定位
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```css
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/* 1号项目就是从第二根垂直网格线开始第四根结束 */
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.item1 {
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grid-column-start: 2;
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grid-column-end: 4;
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background: red;
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}
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```
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# 硬件加速(IE9+)
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> 移动端开启,吃内存、增加耗电
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`animation`、`transform`、`transition`不会自动开启`GPU`加速，利用`transform: translateZ(0)` 就可以开启`3D变换`，出发硬件加速
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场景：`webKit内核`偶尔页面闪烁：`transform: translate3d(0, 0, 0);`
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# 控制台打印 shield 徽章
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```js
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console.log(
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"%c" +
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eval("'mozzie.com'") +
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"%cv" +
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eval("'2.0.0'") +
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"%c\r\n" +
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eval("'了解更多:https://www.mozzie.com'"),
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"color: #fff; background: #5281FA; font-size: 12px;border-radius:2px 0 0 2px;padding:3px 6px;",
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"border-radius:0 2px 2px 0;padding:3px 6px;color:#333;background:#EBEBEB",
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"margin-top:10px;"
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);
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```
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# css 判断 input 是否为空
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`:placeholder-shown`：占位符是否显示的伪类，配合 `:not()` （不是必须，反过来也可以）
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```html
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<div id="demo">
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<input id="demo-input" type="text" placeholder="name" />
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<label id="demo-label">Name</label>
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</div>
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```
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```css
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#demo {
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width: 90%;
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max-width: 450px;
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position: relative;
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}
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#demo-input {
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width: 100%;
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height: 60px;
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line-height: 60px;
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font-size: 20px;
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border-bottom: 1px solid #ffa500;
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}
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#demo-input::placeholder {
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font-size: 0;
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}
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#demo-input:focus + label,
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#demo-input:not(:placeholder-shown) + label {
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top: 0;
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font-size: 12px;
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}
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#demo-label {
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font-size: 22px;
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color: #ffa500;
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position: absolute;
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left: 0;
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top: 50%;
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transform: translateY(-50%);
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transition: all 0.3s;
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}
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/*
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* Default
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*/
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body {
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height: 100vh;
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display: flex;
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}
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body div {
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margin: auto;
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}
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body div input {
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border: 0;
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outline: 0;
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}
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```
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# 居中
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## transform 大法
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```css
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#wrapper {
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position: relative;
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}
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#box {
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position: absolute;
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top: 50%;
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left: 50%;
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transform: translate(-50%, -50%);
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}
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```
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## 0000 大法
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```css
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#wrapper {
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position: relative;
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}
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#box {
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position: absolute;
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top: 0;
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left: 0;
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right: 0;
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bottom: 0;
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}
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```
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## 如何让 img 垂直居中
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```html
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<div id="imgWrapper">
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<img src="xxx.png" />
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</div>
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```
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```css
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.imgWrapper {
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display: table-cell;
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text-align: center;
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vertical-align: middle;
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}
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```
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## ul 下 li 居中
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```html
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<!--外层包个div/section block元素 -->
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<div>
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<ul class="clearfix">
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<li>1</li>
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<li>2</li>
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</ul>
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</div>
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```
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```css
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div{
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text-align: center
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}
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ul{
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display: inline-block
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}
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li{
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display: inline
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float: left
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}
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```
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# js 随机渐变背景
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```javascript
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function getRandomRangeNum(min, max) {
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return min + Math.floor(Math.random() * (max - min));
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}
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function setRandomBg(el) {
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var left = getRandomRangeNum(0, 255);
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var bottom = getRandomRangeNum(0, 255);
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var css = [
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"linear-gradient(to left bottom,hsl(",
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left,
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", 100%, 85%) 0%,hsl(",
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bottom,
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", 100%, 85%) 100%)",
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];
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el.style.background = css.join("");
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}
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```
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# css 三角形
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```css
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span {
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width: 0;
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height: 0;
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border-top: 40px solid transparent;
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border-left: 40px solid transparent;
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border-right: 40px solid transparent;
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border-bottom: 40px solid #ff0000;
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}
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```
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# 1px 神迹
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## pc 端最优解
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```html
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<div style="height:1px;overflow:hidden;background:red"></div>
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```
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## 移动端 - 媒体查询 + transform
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```css
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@media only screen and (-webkit-min-device-pixel-ratio: 2) {
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.border-bottom::after {
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-webkit-transform: scaleY(0.5);
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transform: scaleY(0.5);
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}
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}
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```
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## 移动端 - 媒体查询 + 伪类
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```css
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.border__1px:before {
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content: '';
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position: absolute;
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top: 0;
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height: 1px;
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width: 100%
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background-color: #000;
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transform-origin: 50% 0%;
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}
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@media only screen and (-webkit-min-device-pixel-ratio:2) {
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.border__1px:before {
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transform: scaleY(0.5)
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}
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}
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@media only screen and (-webkit-min-device-pixel-ratio:3) {
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.border__1px:before {
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transform: scaleY(0.33)
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}
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}
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```
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# 横竖屏适配
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js 检测
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```js
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window.addEventListener("resize", () => {
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if (window.orientation === 180 || window.orientation === 0) {
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// 正常方向或屏幕旋转180度
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console.log("竖屏");
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}
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if (window.orientation === 90 || window.orientation === -90) {
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// 屏幕顺时钟旋转90度或屏幕逆时针旋转90度
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console.log("横屏");
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}
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});
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```
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css 检测
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```css
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@media screen and (orientation: portrait) {
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/*竖屏...*/
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}
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@media screen and (orientation: landscape) {
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/*横屏...*/
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}
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```
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# 像素
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- 物理像素: 物理设备真实的像素
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- 独立像素: 平时开发写的 px
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- 设备像素比(DPR): = 物理像素 / 设备独立像素
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```js
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// 获取 DPR
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window.devicePixelRatio;
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```
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也可以使用媒体查询
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```css
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@media (-webkit-min-device-pixel-ratio: 2), (min-device-pixel-ratio: 2) {
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}
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```
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# srcset
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使用 img 标签的 `srcset` 属性，浏览器会自动根据像素密度匹配最佳显示图片：
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```html
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<img src="conardLi_1x.png" srcset="conardLi_2x.png 2x, conardLi_3x.png 3x" />
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```
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# 字体小于 12px
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css3 的 `transform` 属性，设置值为 `scale(x, y)` 定义 2D 缩放转换
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# css 清浮动
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```css
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.clearfix::after {
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content: "";
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display: block;
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clear: both;
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}
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```
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# ellipsis
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## 单行
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```css
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.ellipsis {
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overflow: hidden;
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text-overflow: ellipsis;
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white-space: nowrap;
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}
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```
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## 多行
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```css
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.ellipsis {
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display: -webkit-box;
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-webkit-box-orient: vertical;
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-webkit-line-clamp: 3; // 最多显示几行
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overflow: hidden;
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}
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```
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# 页面导入样式时，使用 link 和 @import
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> 你可能不信，ie5+就支持@import 了
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- link: 与`dom`异步加载
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- @import: 先加载`dom`
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# em | rem 换算
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相对于HTML根元素 `font-size` 来确定的，浏览器的默认字体高是 `16px`，因此:
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- 16px = 1em
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- 12px = .75em
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- 10px = .625em
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简化 rem 到 px 的换算，因为每个 rem 单位都是 10px 的倍数
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```css
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html {
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font-size: 62.5%; /* 这会将默认的 16px 缩小为 10px */
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}
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```
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也可以使用 js 检测设置
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```js
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// set 1rem = viewWidth / 10
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function setRemUnit() {
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var docEl = document.documentElement;
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var rem = docEl.clientWidth / 10;
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docEl.style.fontSize = rem + "px";
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}
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window.addEventListener("resize", setRemUnit);
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window.addEventListener("pageShow", function (e) {
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if (e.persisted) setRemUnit()
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});
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```
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# less 常用
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## 变量
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LESS 中的变量为完全的 `常量` ，所以只能定义一次
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```less
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@nice-blue: #5B83AD;
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@light-blue: @nice-blue + #111;
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#header {
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color: @light-blue;
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}
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```
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输出
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```less
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#header {
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color: #6c94be;
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}
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```
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## 混合
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```less
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.bordered {
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border-top: dotted 1px black;
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border-bottom: solid 2px black;
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}
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```
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使用
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```less
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#menu a {
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color: #111;
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.bordered;
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}
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.post a {
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color: red;
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.bordered;
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}
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```
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带参
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```less
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.border-radius (@radius) {
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border-radius: @radius;
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-moz-border-radius: @radius;
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-webkit-border-radius: @radius;
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}
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```
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#header {
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.border-radius(4px);
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}
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`@arguments`变量，包含了所有传递进来的参数. 如果你不想单独处理每一个参数
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```less
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.box-shadow (@x: 0, @y: 0, @blur: 1px, @color: #000) {
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box-shadow: @arguments;
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-moz-box-shadow: @arguments;
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-webkit-box-shadow: @arguments;
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}
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.box-shadow(2px, 5px);
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```
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无参
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```less
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.wrap () {
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text-wrap: wrap;
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white-space: pre-wrap;
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white-space: -moz-pre-wrap;
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word-wrap: break-word;
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}
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pre {
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.wrap;
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}
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```
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## lighten 和 darken
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```less
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@color-base: #3bafda;
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@color-hover:lighten (@color-primary,10%);
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@color-focus:darken (@color-primary,10%);
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```
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## contrast
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选择两种颜色中哪一种颜色与另一种颜色形成最大对比。
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```less
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p {
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a: contrast(#bbbbbb); //output: black
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b: contrast(#222222, #101010); //output: white
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}
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```
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## JavaScript 表达式
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```less
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@var: ` "hello" .toUpperCase() + "!" `;
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@height: `document.body.clientHeight`;
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```
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## & 父选择器
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`&` 只能代表父元素，不能代表父亲的父辈元素，施加改性类或伪类
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```less
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a {
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color: blue;
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&:hover {
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color: green;
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}
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}
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```
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## 重复父类名
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```less
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.button {
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&-ok {
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background-image: url("ok.png");
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}
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&-cancel {
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background-image: url("cancel.png");
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}
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&-custom {
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background-image: url("custom.png");
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}
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}
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```
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