---
title: CanvasRenderingContext2D.measureText()
slug: Web/API/CanvasRenderingContext2D/measureText
tags:
  - API
  - Canvas
  - CanvasRenderingContext2D
translation_of: Web/API/CanvasRenderingContext2D/measureText
---
<div>{{APIRef}}</div>

<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code><span>.measureText()</span></code></strong> 方法返回一个关于被测量文本{{domxref("TextMetrics")}} 对象包含的信息（例如它的宽度）。</p>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="syntaxbox"><var><em>ctx</em></var>.measureText(text);</pre>

<h3 id="参数">参数</h3>

<dl>
 <dt>text</dt>
 <dd>需要测量的{{jsxref("String")}} 。</dd>
</dl>

<h3 id="返回值">返回值</h3>

<p>{{domxref("TextMetrics")}} 对象。</p>

<h2 id="示例">示例</h2>

<p>给出 {{HTMLElement("canvas")}} 元素：</p>

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

<p>使用下面的代码，你能得到 {{domxref("TextMetrics")}} 对象：</p>

<pre class="brush: js">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-context-2d-measuretext", "CanvasRenderingContext2D.measureText")}}</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>

<p>{{Compat("api.CanvasRenderingContext2D.measureText")}}</p>

<h2 id="See_Also" name="See_Also">参见</h2>

<ul>
 <li>接口定义， {{domxref("CanvasRenderingContext2D")}}.</li>
 <li>{{domxref("TextMetrics")}}</li>
</ul>