---
title: Range.setStart()
slug: Web/API/Range/setStart
translation_of: Web/API/Range/setStart
---
<p>{{ApiRef("DOM")}}</p>

<p> <strong><code>Range.setStart()</code></strong> 方法用于设置 {{ domxref("Range") }}的开始位置。</p>

<p>如果起始节点类型是 <code>Text</code>， <code>Comment</code>, or <code>CDATASection</code>之一, 那么 <code>startOffset指的是</code>从起始节点算起字符的偏移量。 对于其他 <code>Node</code> 类型节点， <code>startOffset</code> 是指从起始结点开始算起子节点的偏移量。</p>

<p> 如果设置的起始位点在结束点之下（在文档中的位置），将会导致选区折叠，起始点和结束点都会被设置为指定的起始位置。</p>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="syntaxbox"><em>range</em>.setStart(<em>startNode</em>, <em>startOffset</em>);
</pre>

<h3 id="Parameters" name="Parameters">参数</h3>

<dl>
 <dt><em>startNode</em></dt>
 <dd>{{ domxref("startNode") }} 用于设定 {{ domxref("Range") }}的起始位置。</dd>
 <dt><em>startOffset</em><code> </code></dt>
 <dd> 必须为不小于0的整数。表示从<code>startNode</code>的开始位置算起的偏移量。</dd>
</dl>

<h2 id="Example" name="Example">例子</h2>

<pre class="brush: js">var range = document.createRange();
var startNode = document.getElementsByTagName("p").item(2);
var startOffset = 0;
range.setStart(startNode,startOffset);
</pre>

<h2 id="Specification" name="Specification">规范</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('DOM WHATWG', '#dom-range-setstart', 'Range.setStart()')}}</td>
   <td>{{Spec2('DOM WHATWG')}}</td>
   <td>No change.</td>
  </tr>
  <tr>
   <td>{{SpecName('DOM2 Traversal_Range', 'ranges.html#Level2-Range-method-setStart', 'Range.setStart()')}}</td>
   <td>{{Spec2('DOM2 Traversal_Range')}}</td>
   <td>Initial specification.</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<p>{{CompatibilityTable}}</p>

<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>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoDesktop("1.0")}}</td>
   <td>9.0</td>
   <td>9.0</td>
   <td>{{CompatVersionUnknown}}</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>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoMobile("1.0")}}</td>
   <td>9.0</td>
   <td>9.0</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="参见">参见</h2>

<ul>
 <li><a href="/en-US/docs/DOM/DOM_Reference" title="/en-US/docs/DOM/DOM_Reference">The DOM interfaces index</a></li>
</ul>