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---
title: 自增 (++)
slug: Web/JavaScript/Reference/Operators/Increment
tags:
- JavaScript
- Operator
- Reference
translation_of: Web/JavaScript/Reference/Operators/Increment
---
<div>{{jsSidebar("Operators")}}</div>
<p>自增运算符 (<code>++</code>) 将其操作数递增（加1）并返回一个值。</p>
<div>{{EmbedInteractiveExample("pages/js/expressions-increment.html")}}</div>
<h2 id="语法">语法</h2>
<pre class="syntaxbox notranslate"><strong>Operator:</strong> <var>x</var>++ or ++<var>x</var>
</pre>
<h2 id="描述">描述</h2>
<p>如使用后置（Postfix）自增，操作符在操作数后（例如 <code><var>x</var>++</code>）， 操作数将在自增前返回。</p>
<p>如使用前置（Prefix）自增，操作符在操作数前（例如 <code>++<var>x</var></code>）， 操作数将先自增后返回。</p>
<h2 id="示例">示例</h2>
<h3 id="后置自增Postfix_increment">后置自增(Postfix increment)</h3>
<pre class="brush: js notranslate">let x = 3;
y = x++;
// y = 3
// x = 4
</pre>
<h3 id="前置自增Prefix_increment">前置自增(Prefix increment)</h3>
<pre class="brush: js notranslate">let a = 2;
b = ++a;
// a = 3
// b = 3
</pre>
<h2 id="规范">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-postfix-increment-operator', 'Increment operator')}}</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p>{{Compat("javascript.operators.increment")}}</p>
<h2 id="相关链接">相关链接</h2>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Addition">Addition operator</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Subtraction">Subtraction operator</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Division">Division operator</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Multiplication">Multiplication operator</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Remainder">Remainder operator</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Exponentiation">Exponentiation operator</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Decrement">Decrement operator</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Unary_negation">Unary negation operator</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Unary_plus">Unary plus operator</a></li>
</ul>
<div id="gtx-trans" style="position: absolute; left: 126px; top: 21px;">
<div class="gtx-trans-icon"></div>
</div>
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