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---
title: unload
slug: Web/API/Window/unload_event
tags:
- Window
- events
- unload
translation_of: Web/API/Window/unload_event
original_slug: Web/Events/unload
---
<p>{{APIRef}}</p>
<p>当文档或一个子资源正在被卸载时, 触发 <strong>unload</strong>事件。</p>
<table class="properties">
<tbody>
<tr>
<th scope="row">可冒泡（Bubbles）</th>
<td>No</td>
</tr>
<tr>
<th scope="row">可取消（Cancelable）</th>
<td>No</td>
</tr>
<tr>
<th scope="row">接口（Interface）</th>
<td>{{domxref("Event")}}</td>
</tr>
<tr>
<th scope="row">事件处理程序属性（Event handler property）</th>
<td>{{domxref("WindowEventHandlers/onunload", "onunload")}}</td>
</tr>
</tbody>
</table>
<p>它在下面两个事件后被触发:</p>
<ol>
<li><a href="/en-US/docs/Mozilla_event_reference/beforeunload" title="/en-US/docs/Mozilla_event_reference/beforeunload">beforeunload</a> (可取消默认行为的事件)</li>
<li><a href="/en-US/docs/Mozilla_event_reference/pagehide" title="/en-US/docs/Mozilla_event_reference/pagehide">pagehide</a></li>
</ol>
<p>文档处于以下状态：</p>
<ul>
<li>所有资源仍存在 (图片, iframe 等.)</li>
<li>对于终端用户所有资源均不可见</li>
<li>界面交互无效 (<code>window.open</code>, <code>alert</code>, <code>confirm</code> 等.)</li>
<li>错误不会停止卸载文档的过程</li>
</ul>
<p>请注意<code>unload</code>事件也遵循文档树:父iframe会在子iframe卸载前卸载(参考下面的例子).</p>
<h2 id="示例">示例</h2>
<pre class="brush: html notranslate"><!DOCTYPE html>
<html>
<head>
<title>Parent Frame</title>
<script>
window.addEventListener('beforeunload', function(event) {
console.log('I am the 1st one.');
});
window.addEventListener('unload', function(event) {
console.log('I am the 3rd one.');
});
</script>
</head>
<body>
<iframe src="child-frame.html"></iframe>
</body>
</html></pre>
<p>下面是 <code>child-frame.html的内容</code>:</p>
<pre class="brush: html notranslate"><!DOCTYPE html>
<html>
<head>
<title>Child Frame</title>
<script>
window.addEventListener('beforeunload', function(event) {
console.log('I am the 2nd one.');
});
window.addEventListener('unload', function(event) {
console.log('I am the 4th and last one…');
});
</script>
</head>
<body>
☻
</body>
</html></pre>
<p>当父iframe被卸载，事件将按<code>console.log()</code> 消息描述的顺序触发。</p>
<h2 id="规范">规范</h2>
<table>
<thead>
<tr>
<th scope="col">规范</th>
<th scope="col">状态</th>
<th scope="col">描述</th>
</tr>
</thead>
<tbody>
<tr>
<td>{{SpecName('UI Events', '#event-type-unload', 'unload')}}</td>
<td>{{Spec2('UI Events')}}</td>
<td></td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p>{{Compat("api.Window.unload_event")}}</p>
<h2 id="参见">参见</h2>
<ul>
<li>相关事件： {{domxref("Window/DOMContentLoaded_event", "DOMContentLoaded")}}, {{domxref("Document/readystatechange_event", "readystatechange")}}, {{domxref("Window/load_event", "load")}}</li>
<li><a href="https://html.spec.whatwg.org/multipage/browsers.html#unloading-documents">Unloading Documents — unload a document</a></li>
</ul>
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