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---
title: Subtraction assignment (-=)
slug: Web/JavaScript/Reference/Operators/Subtraction_assignment
translation_of: Web/JavaScript/Reference/Operators/Subtraction_assignment
---
<div>{{jsSidebar("Operators")}}</div>
<p>The subtraction assignment operator (<code>-=</code>) subtracts the value of the right operand from a variable and assigns the result to the variable.</p>
<div>{{EmbedInteractiveExample("pages/js/expressions-subtraction-assignment.html")}}</div>
<div></div>
<h2 id="语法">语法</h2>
<pre class="syntaxbox notranslate"><strong>Operator:</strong> x -= y
<strong>Meaning:</strong> x = x - y</pre>
<h2 id="Examples">Examples</h2>
<h3 id="Using_subtraction_assignment">Using subtraction assignment</h3>
<pre class="brush: js notranslate">// Assuming the following variable
// bar = 5
bar -= 2 // 3
bar -= 'foo' // NaN</pre>
<h2 id="Specifications">Specifications</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
</tr>
<tr>
<td>{{SpecName('ESDraft', '#sec-assignment-operators', 'Assignment operators')}}</td>
</tr>
</tbody>
</table>
<h2 id="Browser_compatibility">Browser compatibility</h2>
<p>{{Compat("javascript.operators.subtraction_assignment")}}</p>
<h2 id="See_also">See also</h2>
<ul>
<li><a href="/en-US/docs/Web/JavaScript/Guide/Expressions_and_Operators#Assignment">Assignment operators in the JS guide</a></li>
<li><a href="/en-US/docs/Web/JavaScript/Reference/Operators/Subtraction">Subtraction operator</a></li>
</ul>
<p>
<audio style="display: none;"></audio>
</p>
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