---
title: Firefox 31 for developers
slug: Mozilla/Firefox/Releases/31
translation_of: Mozilla/Firefox/Releases/31
---
<div>{{FirefoxSidebar}}</div><p><span style="font-size: 30px; font-weight: 700; letter-spacing: -1px; line-height: 30px;">Web 开发者需要关注的变化</span></p>
<h3 id="Developer_Tools">Developer Tools</h3>
<p><em>No change.</em></p>
<h3 id="CSS">CSS</h3>
<ul>
 <li>CSS变量的语法从旧的 "var-" 前缀更新为新的 "--" 前缀.({{Bug(985838)}})</li>
 <li>Unwanted white space for multiple of 10,000 in Korean counte.({{Bug(985186)}})</li>
</ul>
<h3 id="HTML">HTML</h3>
<p><em>No change.</em></p>
<h3 id="JavaScript">JavaScript</h3>
<p>实现了如下 ECMAScript 6 新特性:</p>
<ul>
 <li><code>Array</code> 方法: {{jsxref("Array.prototype.fill()")}} ({{Bug(911147)}})</li>
 <li><code>Math</code> 函数: {{jsxref("Math.clz32()")}} ({{Bug(925123)}})</li>
 <li><code>String</code> 方法: {{jsxref("String.prototype.normalize()")}} ({{Bug(918987)}}).</li>
</ul>
<h3 id="InterfacesAPIsDOM">Interfaces/APIs/DOM</h3>
<ul>
 <li>Constructor of <code>KeyboardEvent</code> has been implemented ({{Bug(930893)}}).</li>
 <li><code>KeyboardEvent.initKeyboardEvent()</code> has been implemented ({{Bug(930893)}}).</li>
 <li><code>KeyboardEvent.isComposing</code> attribute has been implemented ({{Bug(993234)}}).</li>
 <li><code>InputEvent</code> interface has been implemented ({{Bug(993253)}}).</li>
 <li><code>InputEvent.isComposing</code> attribute has been implemented ({{Bug(993253)}}).</li>
</ul>
<h3 id="MathML">MathML</h3>
<p><em>No change.</em></p>
<h3 id="SVG">SVG</h3>
<p><em>No change.</em></p>
<h3 id="AudioVideo">Audio/Video</h3>
<p><em>No change.</em></p>
<h2 id="Security">Security</h2>
<p><em>No change.</em></p>
<h2 id="Changes_for_add-on_and_Mozilla_developers">Changes for add-on and Mozilla developers</h2>
<p><em>No change.</em></p>
<h2 id="See_also">See also</h2>
<ul>
 <li><a href="/en-US/docs/Mozilla/Firefox/Releases/31/Site_Compatibility">Site Compatibility for Firefox 31</a></li>
</ul>
<h3 id="Older_versions">Older versions</h3>
<p>{{Firefox_for_developers('30')}}</p>