---
title: break
slug: Web/JavaScript/Reference/Statements/break
tags:
  - JavaScript
  - Statement
translation_of: Web/JavaScript/Reference/Statements/break
---
<p>{{jsSidebar("Statements")}}</p>

<p><strong>break 陳述句</strong>會中斷目前的迭代、{{jsxref("Statements/switch", "switch")}} 或 {{jsxref("Statements/label", "label")}} 陳述句，並將程式流程轉到被中斷之陳述句後的陳述句。</p>

<div>{{EmbedInteractiveExample("pages/js/statement-break.html")}}</div>



<h2 id="語法">語法</h2>

<pre class="syntaxbox"><code>break [<em>label</em>];</code></pre>

<dl>
 <dt><code>label</code></dt>
 <dd>可選的。欲中斷陳述句的標籤 (label) 識別。若不是要中斷迭代或 {{jsxref("Statements/switch", "switch")}}，則需加此參數。</dd>
</dl>

<h2 id="說明">說明</h2>

<p>中斷陳述 <code>break</code> 可加上標籤 (label) 參數，使其跳出被標籤的陳述語句。此中斷陳述 <code>break</code> 必須被包含在被標籤的陳述語句中。被標籤的陳述語句可被添加於任一個區塊 (<a class="internal" href="/en-US/docs/JavaScript/Reference/Statements/block" title="JavaScript/Reference/Statements/Block">block</a>) 前，而非限定在迴圈陳述。</p>

<h2 id="範例">範例</h2>

<p>下面函式包含一個中斷陳述 <code>break</code> ，當 <code>i</code> 值為 3 時，中斷 <code>while</code> 迴圈，並回傳 <code>3 * x</code> 。</p>

<pre class="brush:js;highlight:[6];">function testBreak(x) {
  var i = 0;

  while (i &lt; 6) {
    if (i == 3) {
      break;
    }
    i += 1;
  }

  return i * x;
}</pre>

<p>The following code uses <code>break</code> statements with labeled blocks. A <code>break</code> statement must be nested within any label it references. Notice that <code>inner_block</code> is nested within <code>outer_block</code>.</p>

<pre class="brush:js;highlight:[1,2,4];">outer_block: {
  inner_block: {
    console.log('1');
    break outer_block; // breaks out of both inner_block and outer_block
    console.log(':-('); // skipped
  }
  console.log('2'); // skipped
}
</pre>

<p>The following code also uses <code>break</code> statements with labeled blocks but generates a Syntax Error because its <code>break</code> statement is within <code>block_1</code> but references <code>block_2</code>. A <code>break</code> statement must always be nested within any label it references.</p>

<pre class="brush:js;highlight:[1,3,6];">block_1: {
  console.log('1');
  break block_2; // SyntaxError: label not found
}

block_2: {
  console.log('2');
}
</pre>

<h2 id="規範">規範</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('ES1')}}</td>
   <td>{{Spec2('ES1')}}</td>
   <td>Initial definition. Unlabeled version.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES3')}}</td>
   <td>{{Spec2('ES3')}}</td>
   <td>Labeled version added.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-12.8', 'Break statement')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-break-statement', 'Break statement')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-break-statement', 'Break statement')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="瀏覽器相容性">瀏覽器相容性</h2>



<p>{{Compat("javascript.statements.break")}}</p>

<h2 id="參見">參見</h2>

<ul>
 <li>{{jsxref("Statements/continue", "continue")}}</li>
 <li>{{jsxref("Statements/label", "label")}}</li>
 <li>{{jsxref("Statements/switch", "switch")}}</li>
</ul>