From 33058f2b292b3a581333bdfb21b8f671898c5060 Mon Sep 17 00:00:00 2001
From: Peter Bengtsson <mail@peterbe.com>
Date: Tue, 8 Dec 2020 14:40:17 -0500
Subject: initial commit

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+---
+title: PerformanceObserver.observe()
+slug: Web/API/PerformanceObserver/observe
+tags:
+  - 性能
+  - 性能监测对象
+  - 接口
+translation_of: Web/API/PerformanceObserver/observe
+---
+<div>{{APIRef("Performance Timeline API")}}</div>
+
+<p>{{domxref("PerformanceObserver", "性能监测对象")}} 的 <strong><code>observe()</code></strong> 方法用于观察传入的参数中指定的性能条目类型的集合。当记录一个指定类型的性能条目时，性能监测对象的回调函数将会被调用。</p>
+
+<h2 id="语法">语法</h2>
+
+<pre class="syntaxbox"><em>observer</em>.observe(<em>options</em>);
+</pre>
+
+<h3 id="参数">参数</h3>
+
+<p> </p>
+
+<dl>
+ <dt><em>options</em></dt>
+ <dd>一个只装了单个键值对的对象，该键值对的键名规定为 <code>entryTypes</code>。<code>entryTypes</code> 的取值要求如下:</dd>
+</dl>
+
+<ul>
+ <li><code>entryTypes</code> 的值：一个放字符串的数组，字符串的有效值取值在{{domxref("PerformanceEntry.entryType", "性能条目类型")}} 中有详细列出。如果其中的某个字符串取的值无效，浏览器会自动忽略它。</li>
+ <li>另：若未传入 <code>options</code> 实参，或传入的 <code>options</code> 实参为空数组，会抛出 {{jsxref("TypeError")}}。</li>
+</ul>
+
+<dl>
+ <dt> </dt>
+</dl>
+
+<h2 id="示例">示例</h2>
+
+<pre class="brush: js">/* 写法一 */
+
+//直接往PerformanceObserver()入参匿名回调函数，成功new了一个PerformanceObserver类的，名为observer的对象
+var observer = new PerformanceObserver(function(list, obj) {
+  var entries = list.getEntries();
+  for (var i=0; i &lt; entries.length; i++) {
+    //处理 “mark” 和 “frame” 事件
+  }
+});
+//调用observer对象的observe()方法
+observer.observe({entryTypes: ["mark", "frame"]});
+
+/* 写法二 */
+
+//预先声明回调函数perf_observer
+function perf_observer(list, observer) {
+  //处理 “measure” 事件
+}
+//再将其传入PerformanceObserver()，成功new了一个PerformanceObserver类的，名为observer2的对象
+var observer2 = new PerformanceObserver(perf_observer);
+//调用observer2对象的observe()方法
+observer2.observe({entryTypes: ["measure"]});
+</pre>
+
+<h2 id="规范">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('Performance Timeline Level 2', '#dom-performanceobserver-observe', 'observe()')}}</td>
+   <td>{{Spec2('Performance Timeline Level 2')}}</td>
+   <td>Initial definition of <code>observe()</code> method.</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 (WebKit)</th>
+  </tr>
+  <tr>
+   <td>Basic support</td>
+   <td>{{CompatChrome(52.0)}}</td>
+   <td>{{CompatGeckoDesktop(57)}}</td>
+   <td>{{CompatNo}}</td>
+   <td>{{CompatOpera("39")}}</td>
+   <td>{{CompatNo}}</td>
+  </tr>
+ </tbody>
+</table>
+</div>
+
+<div id="compat-mobile">
+<table class="compat-table">
+ <tbody>
+  <tr>
+   <th>Feature</th>
+   <th>Android</th>
+   <th>Android Webview</th>
+   <th>Firefox Mobile (Gecko)</th>
+   <th>IE Phone</th>
+   <th>Opera Mobile</th>
+   <th>Safari Mobile</th>
+   <th>Chrome for Android</th>
+  </tr>
+  <tr>
+   <td>Basic support</td>
+   <td>{{CompatNo}}</td>
+   <td>{{CompatNo}}</td>
+   <td>{{CompatGeckoMobile(57)}}</td>
+   <td>{{CompatNo}}</td>
+   <td>
+    <p>{{CompatOperaMobile(39)}}</p>
+   </td>
+   <td>{{CompatNo}}</td>
+   <td>{{CompatChrome(52.0)}}</td>
+  </tr>
+ </tbody>
+</table>
+</div>
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