--- title: Range.setStartBefore() slug: Web/API/Range/setStartBefore translation_of: Web/API/Range/setStartBefore --- <div>{{ApiRef("DOM")}}</div> <p><strong><code>Range.setStartBefore()</code></strong> 方法相对另一个 {{domxref("Node")}}来设置一个{{domxref("Range")}} 的开始位置. {{domxref("Range")}}的开始节点(focusNode)的父节点,和 <code>referenceNode</code>的父节点是同一个.</p> <h2 id="Syntax" name="Syntax">Syntax</h2> <pre class="syntaxbox"><var>range</var>.setStartBefore(<em>referenceNode</em>); </pre> <h3 id="Parameters" name="Parameters">Parameters</h3> <dl> <dt><em>referenceNode</em></dt> <dd>一个{{domxref("Range")}}新的开始位置上的{{domxref("Node")}}.</dd> </dl> <h2 id="Example" name="Example">Example</h2> <pre class="brush:js">var range = document.createRange(); var referenceNode = document.getElementsByTagName("div").item(0); range.setStartBefore(referenceNode); </pre> <h2 id="Specifications" name="Specifications">Specifications</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-setstartbefore', 'Range.setStartBefore()')}}</td> <td>{{Spec2('DOM WHATWG')}}</td> <td>No change.</td> </tr> <tr> <td>{{SpecName('DOM2 Traversal_Range', 'ranges.html#Level2-Range-setStartBefore', 'Range.setStartBefore()')}}</td> <td>{{Spec2('DOM2 Traversal_Range')}}</td> <td>Initial specification.</td> </tr> </tbody> </table> <h2 id="Browser_compatibility">Browser compatibility</h2> <p>{{Compat("api.Range.setStartBefore")}}</p> <h2 id="See_also">See also</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>