---
title: TextMetrics.width
slug: Web/API/TextMetrics/width
translation_of: Web/API/TextMetrics/width
---
<div>{{APIRef("Canvas API")}}</div>

<p>只读的 <code><strong>TextMetrics</strong></code><strong><code><span>.width</span></code></strong> 属性，包含文本先前的宽度（行内盒子的宽度），使用 CSS 像素计算。</p>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="syntaxbox"><var>readonly <em>metrics</em></var>.width;</pre>

<h2 id="示例">示例</h2>

<p>事先给定 {{HTMLElement("canvas")}} 元素：</p>

<pre class="brush: html">&lt;canvas id="canvas"&gt;&lt;/canvas&gt;
</pre>

<p>你可以使用下面的代码得到一个 {{domxref("TextMetrics")}} 对象：</p>

<pre class="brush: js;highlight:[5]">var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

var text = ctx.measureText("foo"); // TextMetrics object
text.width; // 16;
</pre>

<h2 id="规范描述">规范描述</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('HTML WHATWG', "scripting.html#dom-textmetrics-width", "TextMetrics.width")}}</td>
   <td>{{Spec2('HTML WHATWG')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>4.0</td>
   <td>{{CompatGeckoDesktop("1.8")}}</td>
   <td>9.0</td>
   <td>9.0</td>
   <td>3.1</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>2.1</td>
   <td>{{CompatGeckoMobile("1.8")}}</td>
   <td>{{CompatUnknown}}</td>
   <td>10.0</td>
   <td>3.2</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="参见">参见</h2>

<ul>
 <li>{{domxref("TextMetrics")}}</li>
</ul>