---
title: 按位与 (&)
slug: Web/JavaScript/Reference/Operators/Bitwise_AND
translation_of: Web/JavaScript/Reference/Operators/Bitwise_AND
original_slug: Web/JavaScript/Reference/Operators/按位与
---
<div>{{jsSidebar("Operators")}}</div>

<p>按位与运算符 (<code>&amp;</code>) 在每个位上返回 <code>1</code> ，这两个操作数对应的位都是 <code>1</code>.</p>

<div>{{EmbedInteractiveExample("pages/js/expressions-bitwise-and.html")}}</div>

<div class="hidden">The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone <a href="https://github.com/mdn/interactive-examples">https://github.com/mdn/interactive-examples</a> and send us a pull request.</div>

<h2 id="语法">语法</h2>

<pre class="syntaxbox"><code><var>a</var> &amp; <var>b</var></code>
</pre>

<h2 id="描述">描述</h2>

<p>操作数被转换为32位整数，并由一系列位（0和1）表示。 超过32位的数字将丢弃其最高有效位。 例如，以下大于32位的整数将被转换为32位整数：</p>

<pre class="brush: js">Before: 11100110111110100000000000000110000000000001
After:              10100000000000000110000000000001</pre>

<p>第一个操作数中的每个位都与第二个操作数中的相应位配对：第一位到第一位，第二位到第二位，依此类推。</p>

<p>将运算符应用于每对位，然后按位构造结果。</p>

<p>与运算的真值表：</p>

<table class="standard-table">
 <thead>
  <tr>
   <th class="header" scope="col">a</th>
   <th class="header" scope="col">b</th>
   <th class="header" scope="col">a AND b</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>0</td>
   <td>0</td>
   <td>0</td>
  </tr>
  <tr>
   <td>0</td>
   <td>1</td>
   <td>0</td>
  </tr>
  <tr>
   <td>1</td>
   <td>0</td>
   <td>0</td>
  </tr>
  <tr>
   <td>1</td>
   <td>1</td>
   <td>1</td>
  </tr>
 </tbody>
</table>

<pre class="brush: js">.    9 (base 10) = 00000000000000000000000000001001 (base 2)
    14 (base 10) = 00000000000000000000000000001110 (base 2)
                   --------------------------------
14 &amp; 9 (base 10) = 00000000000000000000000000001000 (base 2) = 8 (base 10)
</pre>

<p>将任何数字<code>x</code>与<code>0</code>进行按位与运算将得出<code>0</code>。</p>

<h2 id="示例">示例</h2>

<h3 id="使用按位与">使用按位与</h3>

<pre class="brush: js">// 5: 00000000000000000000000000000101
// 2: 00000000000000000000000000000010
5 &amp; 2; // 0</pre>

<h2 id="规范说明">规范说明</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{SpecName('ESDraft', '#prod-BitwiseANDExpression', 'Bitwise AND expression')}}</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>



<p>{{Compat("javascript.operators.bitwise_and")}}</p>

<h2 id="参阅">参阅</h2>

<ul>
 <li><a href="/en-US/docs/Web/JavaScript/Guide/Expressions_and_Operators#Bitwise">Bitwise operators in the JS guide</a></li>
 <li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_AND_assignment">Bitwise AND assignment operator</a></li>
</ul>