path: root/files/zh-cn/web/css/clear/index.html

---
title: clear
slug: Web/CSS/clear
tags:
  - CSS
  - CSS 定位
  - CSS 属性
  - 参考
translation_of: Web/CSS/clear
---
<div>{{CSSRef}}</div>

<p> <strong><code>clear</code></strong> <a href="/en-US/docs/CSS" title="CSS">CSS</a> 属性指定一个元素是否必须移动(清除浮动后)到在它之前的浮动元素下面。<code>clear</code> 属性适用于浮动和非浮动元素。</p>

<div>{{EmbedInteractiveExample("pages/css/clear.html")}}</div>



<p>当应用于非浮动块时，它将非浮动块的<a href="/en-US/docs/CSS/box_model" title="CSS/box_model">边框边界</a>移动到所有相关浮动元素<a href="/en-US/docs/CSS/box_model" title="CSS/box_model">外边界</a>的下方。这个非浮动块的<a href="/en-US/docs/CSS/margin_collapsing">垂直外边距</a>会折叠。</p>

<p>另一方面，两个浮动元素的垂直外边距将不会折叠。当应用于浮动元素时，它将元素的<a href="/en-US/docs/CSS/box_model" title="CSS/box_model">外边界</a>移动到所有相关的浮动元素<a href="/en-US/docs/CSS/box_model" title="CSS/box_model">外边框边界</a>的下方。这会影响后面浮动元素的布局，后面的浮动元素的位置无法高于它之前的元素。</p>

<p>要被清除的相关浮动元素指的是在相同<a href="https://developer.mozilla.org/en-US/docs/CSS/block_formatting_context" title="CSS/block_formatting_context">块级格式化上下文</a>中的前置浮动。</p>

<div class="note">
<p><strong>注意：</strong>如果一个元素里只有浮动元素，那它的高度会是0。如果你想要它自适应即包含所有浮动元素，那你需要清除它的子元素。一种方法叫做<strong>clearfix</strong>，即<code>clear</code>一个不浮动的 {{cssxref("::after")}} <a href="/en-US/docs/Web/CSS/Pseudo-elements">伪元素</a>。</p>

<pre><code>#container::after {
  content: "";
  display: block;
  clear: both;
}</code>
</pre>
</div>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="twopartsyntaxbox"><code>/* Keyword values */
clear: none;
clear: left;
clear: right;
clear: both;
clear: inline-start;
clear: inline-end;

/* Global values */
clear: inherit;
clear: initial;
clear: unset;</code></pre>

<h3 id="Values" name="Values">值</h3>

<dl>
 <dt><code>none</code></dt>
 <dd>元素<em>不会</em>向下移动清除之前的浮动。</dd>
 <dt><code>left</code></dt>
 <dd>元素被向下移动用于清除之前的左浮动。</dd>
 <dt><code>right</code></dt>
 <dd>元素被向下移动用于清除之前的右浮动。</dd>
 <dt><code>both</code></dt>
 <dd>元素被向下移动用于清除之前的左右浮动。</dd>
 <dt><code>inline-start</code></dt>
 <dd>该关键字表示该元素向下移动以清除其包含块的起始侧上的浮动。即在某个区域的左侧浮动或右侧浮动。</dd>
 <dt><code>inline-end</code></dt>
 <dd>该关键字表示该元素向下移动以清除其包含块的末端的浮点，即在某个区域的右侧浮动或左侧浮动。</dd>
 <dt>
 <h3 id="Formal_syntax">Formal syntax</h3>

 <pre>{{csssyntax}}</pre>
 </dt>
</dl>

<h2 id="Examples" name="Examples">示例</h2>

<h3 id="clear_left" name="clear:_left">clear: left</h3>

<h4 id="HTML">HTML</h4>

<pre class="brush: html"><code>&lt;div class="wrapper"&gt;
  &lt;p class="black"&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Phasellus sit amet diam. Duis mattis varius dui. Suspendisse eget dolor.&lt;/p&gt;
  &lt;p class="red"&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit.&lt;/p&gt;
  &lt;p class="left"&gt;This paragraph clears left.&lt;/p&gt;
&lt;/div&gt;</code></pre>

<h4 id="CSS">CSS</h4>

<pre class="brush: css"><code>.wrapper{
  border:1px solid black;
  padding:10px;
}
.left {
  border: 1px solid black;
  clear: left;
}
.black {
  float: left;
  margin: 0;
  background-color: black;
  color: #fff;
  width: 20%;
}
.red {
  float: left;
  margin: 0;
  background-color: pink;
  width:20%;
}
p {
  width: 50%;
}</code></pre>

<p>{{ EmbedLiveSample('clear:_left','100%','250') }}</p>

<h3 id="clear_right" name="clear:_right">clear: right</h3>

<h4 id="HTML_2">HTML</h4>

<pre class="brush: html"><code>&lt;div class="wrapper"&gt;
  &lt;p class="black"&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Phasellus sit amet diam. Duis mattis varius dui. Suspendisse eget dolor.&lt;/p&gt;
  &lt;p class="red"&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit.&lt;/p&gt;
  &lt;p class="right"&gt;This paragraph clears right.&lt;/p&gt;
&lt;/div&gt;</code></pre>

<h4 id="CSS_2">CSS</h4>

<pre class="brush: css"><code>.wrapper{
  border:1px solid black;
  padding:10px;
}
.right {
  border: 1px solid black;
  clear: right;
}
.black {
  float: right;
  margin: 0;
  background-color: black;
  color: #fff;
  width:20%;
}
.red {
  float: right;
  margin: 0;
  background-color: pink;
  width:20%;
}
p {
  width: 50%;
}</code></pre>

<p>{{ EmbedLiveSample('clear:_right','100%','250') }}</p>

<h3 id="clear_both" name="clear:_both">clear: both</h3>

<h4 id="HTML_3">HTML</h4>

<pre class="brush: html"><code>&lt;div class="wrapper"&gt;
  &lt;p class="black"&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Phasellus sit amet diam. Duis mattis varius dui. Suspendisse eget dolor. Fusce pulvinar lacus ac dui.&lt;/p&gt;
  &lt;p class="red"&gt;Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Phasellus sit amet diam. Duis mattis varius dui. Suspendisse eget dolor.&lt;/p&gt;
  &lt;p class="both"&gt;This paragraph clears both.&lt;/p&gt;
&lt;/div&gt;</code></pre>

<h4 id="CSS_3">CSS</h4>

<pre class="brush: css"><code>.wrapper{
  border:1px solid black;
  padding:10px;
}
.both {
  border: 1px solid black;
  clear: both;
}
.black {
  float: left;
  margin: 0;
  background-color: black;
  color: #fff;
  width:20%;
}
.red {
  float: right;
  margin: 0;
  background-color: pink;
  width:20%;
}
p {
  width: 45%;
}</code></pre>

<p>{{ EmbedLiveSample('clear:_both','100%','300') }}</p>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{SpecName('CSS Logical Properties', '#float-clear', 'float and clear')}}</td>
   <td>{{Spec2('CSS Logical Properties')}}</td>
   <td>Adds the values <code>inline-start</code> and <code>inline-end</code></td>
  </tr>
  <tr>
   <td>{{SpecName('CSS2.1', 'visuren.html#flow-control', 'clear')}}</td>
   <td>{{Spec2('CSS2.1')}}</td>
   <td>No significant changes, though details are clarified.</td>
  </tr>
  <tr>
   <td>{{SpecName('CSS1', '#clear', 'clear')}}</td>
   <td>{{Spec2('CSS1')}}</td>
   <td>Initial specification</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility" name="Browser_compatibility">浏览器兼容性</h2>

<p>{{Compat("css.properties.clear")}}</p>

<h2 id="参见">参见</h2>

<ul>
 <li><a href="/en-US/docs/CSS/box_model" title="CSS/box_model">盒模型</a></li>
</ul>