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href="/article/%E6%B7%B1%E5%85%A5Vue3%E6%BA%90%E7%A0%81%EF%BC%8C%E7%9C%8B%E7%9C%8BVue.use%E5%90%8E%E7%A9%B6%E7%AB%9F%E5%8F%91%E7%94%9F%E4%BA%86%E4%BB%80%E4%B9%88%EF%BC%9F.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>深入Vue3源码，看看Vue.use后究竟发生了什么？</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/article/%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3Proxy%E4%B8%8EReflect.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>深入理解Proxy与Reflect</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/article/%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3%E6%B5%8F%E8%A7%88%E5%99%A8%E7%BC%93%E5%AD%98%E6%9C%BA%E5%88%B6.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>深入理解浏览器缓存机制</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/article/%E6%B7%B1%E5%85%A5%E7%90%86%E8%A7%A3%E6%B5%8F%E8%A7%88%E5%99%A8%E8%BF%90%E8%A1%8C%E5%8E%9F%E7%90%86.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>深入理解浏览器运行原理</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><div class="group" data-v-ea943bcb><section class="VPSidebarItem level-0 collapsible collapsed" data-v-ea943bcb data-v-f16f934a><div class="item" role="button" tabindex="0" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><h2 class="text" data-v-f16f934a>学习笔记</h2><div class="caret" role="button" aria-label="toggle section" tabindex="0" data-v-f16f934a><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" viewbox="0 0 24 24" class="caret-icon" data-v-f16f934a><path d="M9,19c-0.3,0-0.5-0.1-0.7-0.3c-0.4-0.4-0.4-1,0-1.4l5.3-5.3L8.3,6.7c-0.4-0.4-0.4-1,0-1.4s1-0.4,1.4,0l6,6c0.4,0.4,0.4,1,0,1.4l-6,6C9.5,18.9,9.3,19,9,19z"></path></svg></div></div><div class="items" data-v-f16f934a><!--[--><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/JavaScript.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>JavaScript基础</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/CSS.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>CSS基础</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/JavaScriptEnhanced.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>JavaScript进阶</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/Front-end%20Engineering.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>前端工程化</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/SSR.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>服务端渲染</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/React.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>React基础</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/React%20Hooks.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>React Hooks</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/Redux.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>Redux</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/React%20Router.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>React Router</p><!--]--></a><!----></div><!----></div><div class="VPSidebarItem level-1 is-link" data-v-f16f934a data-v-f16f934a><div class="item" data-v-f16f934a><div class="indicator" data-v-f16f934a></div><a class="VPLink link link" href="/note/MySQL.html" data-v-f16f934a><!--[--><p class="text" data-v-f16f934a>MySQL</p><!--]--></a><!----></div><!----></div><!--]--></div></section></div><!--]--><!--[--><!--]--></nav></aside><div class="VPContent has-sidebar" id="VPContent" data-v-4b282efc data-v-3d0b81df><div class="VPDoc has-sidebar has-aside" data-v-3d0b81df data-v-f0e11dcf><!--[--><!--]--><div class="container" data-v-f0e11dcf><div class="aside" data-v-f0e11dcf><div class="aside-curtain" data-v-f0e11dcf></div><div class="aside-container" data-v-f0e11dcf><div class="aside-content" data-v-f0e11dcf><div class="VPDocAside" data-v-f0e11dcf data-v-0c849b30><!--[--><!--]--><!--[--><!--]--><div class="VPDocAsideOutline" data-v-0c849b30 data-v-ecb1c3c3><div class="content" data-v-ecb1c3c3><div class="outline-marker" data-v-ecb1c3c3></div><div class="outline-title" data-v-ecb1c3c3>On this page</div><nav aria-labelledby="doc-outline-aria-label" data-v-ecb1c3c3><span class="visually-hidden" id="doc-outline-aria-label" data-v-ecb1c3c3> Table of Contents for current page </span><ul class="root" data-v-ecb1c3c3 data-v-61596211><!--[--><!--]--></ul></nav></div></div><!--[--><!--]--><div class="spacer" data-v-0c849b30></div><!--[--><!--]--><!----><!--[--><!--]--><!--[--><!--]--></div></div></div></div><div class="content" data-v-f0e11dcf><div class="content-container" data-v-f0e11dcf><!--[--><!--]--><!----><main class="main" data-v-f0e11dcf><div style="position:relative;" class="vp-doc _article_%E4%B8%80%E6%96%87%E8%AF%BB%E6%87%82%E4%BC%AA%E7%B1%BB%E4%B8%8E%E4%BC%AA%E5%85%83%E7%B4%A0" data-v-f0e11dcf><div><h1 id="一文读懂伪类与伪元素" tabindex="-1">一文读懂伪类与伪元素 <a class="header-anchor" href="#一文读懂伪类与伪元素" aria-label="Permalink to &quot;一文读懂伪类与伪元素&quot;">​</a></h1><h2 id="🔰-什么是伪类" tabindex="-1">🔰 什么是伪类？ <a class="header-anchor" href="#🔰-什么是伪类" aria-label="Permalink to &quot;🔰 什么是伪类？&quot;">​</a></h2><p>伪类是添加到选择器的 <strong>关键字</strong> ，指定要选择的元素的特殊状态。</p><h3 id="典型的伪类关键字" tabindex="-1">典型的伪类关键字 <a class="header-anchor" href="#典型的伪类关键字" aria-label="Permalink to &quot;典型的伪类关键字&quot;">​</a></h3><p>在大多数情况下，<strong>伪类都与基础选择器搭配使用</strong>，下述是伪类在一些典型场景下的应用。</p><h4 id="hover" tabindex="-1"><code>:hover</code> <a class="header-anchor" href="#hover" aria-label="Permalink to &quot;`:hover`&quot;">​</a></h4><p>指针在 <code>&lt;button&gt;</code> 上悬停，但没有激活它时，按钮颜色变为蓝色</p><div class="language-css line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">css</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#FFCB6B;">button</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">hover</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><blockquote><p><strong>注意</strong>: 在触摸屏上 <code>:hover</code> 基本不可用。不同的浏览器上<code>:hover</code> 伪类表现不同。网页开发人员不要让任何内容只能通过悬停才能展示出来，不然这些内容对于触摸屏使用者来说是很难或者说不可能看到。</p></blockquote><h4 id="not" tabindex="-1"><code>:not</code> <a class="header-anchor" href="#not" aria-label="Permalink to &quot;`:not`&quot;">​</a></h4><p><strong><code>:not()</code></strong> 用来匹配不符合一组选择器的元素。由于它的作用是防止特定的元素被选中，它也被称为<em>反选伪类</em>（<em>negation pseudo-class</em>）。</p><p>将所有不是<code>&lt;p&gt;</code>的元素颜色改为蓝色：</p><div class="language-css line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">css</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#FFCB6B;">body</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">not</span><span style="color:#89DDFF;">(</span><span style="color:#FFCB6B;">p</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">/* 实测下述代码没有效果 */</span></span>
<span class="line"><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">not</span><span style="color:#89DDFF;">(</span><span style="color:#FFCB6B;">p</span><span style="color:#89DDFF;">)</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><blockquote><p><strong>注意</strong>: 在触摸屏上 <code>:hover</code> 基本不可用。不同的浏览器上<code>:hover</code> 伪类表现不同。网页开发人员不要让任何内容只能通过悬停才能展示出来，不然这些内容对于触摸屏使用者来说是很难或者说不可能看到。</p></blockquote><h4 id="first-child" tabindex="-1"><code>:first-child</code> <a class="header-anchor" href="#first-child" aria-label="Permalink to &quot;`:first-child`&quot;">​</a></h4><p>给所有 <code>&lt;ul&gt;</code> 下的第一个 <code>&lt;li&gt;</code> 应用不同的样式</p><div class="language-css line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">css</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#FFCB6B;">ul</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">li</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"><span style="color:#FFCB6B;">ul</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">li</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">first-child</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">font-weight</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> bold</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><h4 id="active" tabindex="-1"><code>:active</code> <a class="header-anchor" href="#active" aria-label="Permalink to &quot;`:active`&quot;">​</a></h4><p><code>:active</code> 表示的是鼠标从按下到松开的时间，下述代码表示 <code>&lt;a&gt;</code> 在不同状态下的样式。</p><div class="language-css line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">css</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#FFCB6B;">a</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">link</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> blue</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">/* 未访问链接 */</span></span>
<span class="line"><span style="color:#FFCB6B;">a</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">visited</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> purple</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">/* 已访问链接 */</span></span>
<span class="line"><span style="color:#FFCB6B;">a</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">hover</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">background</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> yellow</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">/* 用户鼠标悬停 */</span></span>
<span class="line"><span style="color:#FFCB6B;">a</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">active</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">}</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;">/* 激活链接 */</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><blockquote><p><strong>注意</strong>: <code>:active</code> 赋予的样式可能会被后声明的其他链接相关的伪类覆盖。为保证样式生效，需要把 <code>:active</code> 的样式放在所有链接相关的样式之后。</p></blockquote><p>这种链接伪类先后顺序被称为 <em>LVHA 顺序</em>：<code>:link</code> &gt; <code>:visited</code> &gt; <code>:hover</code> &gt; <code>:active</code>。</p><h3 id="单独使用的伪类关键字" tabindex="-1">单独使用的伪类关键字 <a class="header-anchor" href="#单独使用的伪类关键字" aria-label="Permalink to &quot;单独使用的伪类关键字&quot;">​</a></h3><p>我们常见的伪类关键字的特征是以单个冒号<code>:</code>开头，跟随在基础选择器后面。</p><p><strong>但是单独使用的伪类关键字也可以对页面产生效果，</strong> 例如：</p><p>通过 <code>:focus</code> 伪类，可以让任何元素获得焦点后的颜色变为红色。</p><div class="language-css line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">css</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">focus</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> red</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>更多伪类，见 <a href="https://developer.mozilla.org/zh-CN/docs/Web/CSS/Pseudo-classes#%E6%A0%87%E5%87%86%E4%BC%AA%E7%B1%BB%E7%B4%A2%E5%BC%95" target="_blank" rel="noreferrer">MDN - 标准伪类索引</a></p><p><img src="https://p1-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/d77fd1d23840415ca645e9429237b6dc~tplv-k3u1fbpfcp-watermark.image?" alt="image.png"></p><h2 id="🔰-什么是伪元素" tabindex="-1">🔰 什么是伪元素？ <a class="header-anchor" href="#🔰-什么是伪元素" aria-label="Permalink to &quot;🔰 什么是伪元素？&quot;">​</a></h2><p>伪元素是一个<strong>附加至选择器末的关键词</strong>，允许你对被选择元素的特定部分修改样式。</p><p>与伪类相同，一个选择器中只能使用一个伪元素。但是，<strong>伪元素必须紧跟在语句中的基础选择器之后</strong>。</p><p>例如，下述代码可以给页面中每个 <code>&lt;a&gt;</code> 标签前添加一个😃表情。</p><div class="language-css line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">css</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#FFCB6B;">a</span><span style="color:#89DDFF;">::</span><span style="color:#C792EA;">before</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">content</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">😃</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>相比于伪类，伪元素的使用方式更加固定，其基本语法：</p><div class="language-css line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">css</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#A6ACCD;">selector::</span><span style="color:#FFCB6B;">pseudo-element</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">property</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> value</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><blockquote><p><strong>注意</strong>: 在书写伪元素时，你会见到单冒号 <code>:</code> 的写法，但此为CSS2过时语法，仅用于支持IE8，大多情况请书写双冒号 <code>::</code> 来表示伪元素。</p></blockquote><p>更多伪元素见 <a href="https://developer.mozilla.org/zh-CN/docs/Web/CSS/Pseudo-elements#%E6%A0%87%E5%87%86%E4%BC%AA%E5%85%83%E7%B4%A0%E7%B4%A2%E5%BC%95" target="_blank" rel="noreferrer">MDN - 标准伪元素索引</a></p><p><img src="https://p3-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/17049cd3157f4a368c98d4fcd905c064~tplv-k3u1fbpfcp-watermark.image?" alt="image.png"></p><h2 id="📌-伪类与伪元素共同使用" tabindex="-1">📌 伪类与伪元素共同使用 <a class="header-anchor" href="#📌-伪类与伪元素共同使用" aria-label="Permalink to &quot;📌 伪类与伪元素共同使用&quot;">​</a></h2><p>下面一个案例中，同时用到了伪类和伪元素：</p><blockquote><p>用CSS实现一个开关样式，hover时触发，滑块为正方形，具体大小可随意，如下图</p></blockquote><p><img src="https://p6-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/a6e4b09bb9e64989b0561d48d10a2734~tplv-k3u1fbpfcp-watermark.image?" alt="image.png"></p><blockquote><p>尽量实现如下要求，可实现一部分：</p><ol><li>开关动作均有动画过度（滑块移位、背景色）</li><li>只用一个dom元素实现</li><li>开关的高度是固定的，但宽度不固定，即宽度为未知父元素的100%，宽度始终大于高度</li></ol></blockquote><h3 id="题目解读" tabindex="-1">题目解读 <a class="header-anchor" href="#题目解读" aria-label="Permalink to &quot;题目解读&quot;">​</a></h3><p>由于只能使用一个 <code>DOM</code> 元素，而要区分滑块和背景的不同状态，故使用伪元素 <code>::before</code> 在 <code>.box</code> 内部添加一个滑块，滑块采用 <code>inline-block</code> 方式展示，并且由 <code>transition</code> 属性指定过渡动画。</p><p>对于背景也采用了 <code>transition</code> 来指定过渡动画，并且二者都通过 <code>:hover</code> 触发。</p><p><img src="https://p9-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/1ac690e718be445083bc67b7bbcccb7e~tplv-k3u1fbpfcp-watermark.image?" alt="image.png"></p><h3 id="实现代码" tabindex="-1">实现代码 <a class="header-anchor" href="#实现代码" aria-label="Permalink to &quot;实现代码&quot;">​</a></h3><p><code>HTML</code></p><div class="language-html line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">html</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">class</span><span style="color:#89DDFF;">=</span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">father</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&lt;</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;"> </span><span style="color:#C792EA;">class</span><span style="color:#89DDFF;">=</span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">box</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">&gt;&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span>
<span class="line"><span style="color:#89DDFF;">&lt;/</span><span style="color:#F07178;">div</span><span style="color:#89DDFF;">&gt;</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p><code>CSS</code></p><div class="language-css line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">css</span><pre class="shiki material-theme-palenight"><code><span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">box</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">height</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">50px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">100%</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">background-color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">c2d3e4</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">transition</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> background-color </span><span style="color:#F78C6C;">0.25s</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">box</span><span style="color:#89DDFF;">::</span><span style="color:#C792EA;">before</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">content</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">&quot;</span><span style="color:#C3E88D;">b</span><span style="color:#89DDFF;">&quot;</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> white</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">display</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> inline-block</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">background-color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> white</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">position</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> relative</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">top</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">left</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">5%</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">height</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">40px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">35%</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">transition</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> left </span><span style="color:#F78C6C;">0.25s</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">box</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">hover</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">background-color</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">#</span><span style="color:#A6ACCD;">348fe4</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">box</span><span style="color:#89DDFF;">:</span><span style="color:#C792EA;">hover</span><span style="color:#89DDFF;">::</span><span style="color:#C792EA;">before</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">left</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">60%</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#676E95;font-style:italic;">/* 父元素宽度任意 */</span></span>
<span class="line"><span style="color:#89DDFF;">.</span><span style="color:#FFCB6B;">father</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">{</span></span>
<span class="line"><span style="color:#A6ACCD;"> </span><span style="color:#B2CCD6;">width</span><span style="color:#89DDFF;">:</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">100px</span><span style="color:#89DDFF;">;</span></span>
<span class="line"><span style="color:#89DDFF;">}</span></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br></div></div><h3 id="相关链接" tabindex="-1">相关链接 <a class="header-anchor" href="#相关链接" aria-label="Permalink to &quot;相关链接&quot;">​</a></h3><p><a href="https://code.juejin.cn/pen/7088328950488760334" target="_blank" rel="noreferrer">代码片段</a></p><p><a href="https://developer.mozilla.org/zh-CN/docs/Learn/CSS/Building_blocks/Selectors" target="_blank" rel="noreferrer"><code>CSS选择器</code></a></p></div></div></main><footer class="VPDocFooter" data-v-f0e11dcf data-v-bdb4c5a7><!--[--><!--]--><div class="edit-info" data-v-bdb4c5a7><div class="edit-link" data-v-bdb4c5a7><a class="VPLink link vp-external-link-icon no-icon edit-link-button" href="https://github.com/ZiuChen/ZiuChen.github.io/edit/main/docs/article/一文读懂伪类与伪元素.md" target="_blank" rel="noreferrer" data-v-bdb4c5a7><!--[--><svg xmlns="http://www.w3.org/2000/svg" viewbox="0 0 24 24" class="edit-link-icon" aria-label="edit icon" data-v-bdb4c5a7><path d="M18,23H4c-1.7,0-3-1.3-3-3V6c0-1.7,1.3-3,3-3h7c0.6,0,1,0.4,1,1s-0.4,1-1,1H4C3.4,5,3,5.4,3,6v14c0,0.6,0.4,1,1,1h14c0.6,0,1-0.4,1-1v-7c0-0.6,0.4-1,1-1s1,0.4,1,1v7C21,21.7,19.7,23,18,23z"></path><path d="M8,17c-0.3,0-0.5-0.1-0.7-0.3C7,16.5,6.9,16.1,7,15.8l1-4c0-0.2,0.1-0.3,0.3-0.5l9.5-9.5c1.2-1.2,3.2-1.2,4.4,0c1.2,1.2,1.2,3.2,0,4.4l-9.5,9.5c-0.1,0.1-0.3,0.2-0.5,0.3l-4,1C8.2,17,8.1,17,8,17zM9.9,12.5l-0.5,2.1l2.1-0.5l9.3-9.3c0.4-0.4,0.4-1.1,0-1.6c-0.4-0.4-1.2-0.4-1.6,0l0,0L9.9,12.5z M18.5,2.5L18.5,2.5L18.5,2.5z"></path></svg> Edit this page on GitHub<!--]--></a></div><div class="last-updated" data-v-bdb4c5a7><p class="VPLastUpdated" data-v-bdb4c5a7 data-v-4e6de435>Updated Date: <time datetime="2023-08-09T16:23:59.000Z" data-v-4e6de435></time></p></div></div><nav class="prev-next" data-v-bdb4c5a7><div class="pager" data-v-bdb4c5a7><a class="pager-link prev" href="/article/%E4%B8%80%E6%96%87%E8%AF%BB%E6%87%82%E4%BA%8B%E4%BB%B6%E5%86%92%E6%B3%A1%E4%B8%8E%E4%BA%8B%E4%BB%B6%E6%8D%95%E8%8E%B7.html" data-v-bdb4c5a7><span class="desc" data-v-bdb4c5a7>Previous page</span><span class="title" data-v-bdb4c5a7>一文读懂事件冒泡与事件捕获</span></a></div><div class="pager" data-v-bdb4c5a7><a class="pager-link next" href="/article/%E4%B8%80%E6%96%87%E8%AF%BB%E6%87%82%E5%87%BD%E6%95%B0%E4%B8%ADthis%E6%8C%87%E5%90%91%E9%97%AE%E9%A2%98.html" data-v-bdb4c5a7><span class="desc" data-v-bdb4c5a7>Next page</span><span class="title" data-v-bdb4c5a7>一文读懂函数中this指向问题</span></a></div></nav></footer><!--[--><!--]--></div></div></div><!--[--><!--]--></div></div><footer class="VPFooter has-sidebar" data-v-4b282efc data-v-a21bf57e><div class="container" data-v-a21bf57e><p class="message" data-v-a21bf57e>Released under the MIT License.</p><p class="copyright" data-v-a21bf57e>Copyright © 2019-present Ziu Chen</p></div></footer><!--[--><!--]--></div></div>
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