---
title: PerformanceTiming.requestStart
slug: Web/API/PerformanceTiming/requestStart
translation_of: Web/API/PerformanceTiming/requestStart
---
<p>{{ APIRef("PerformanceTiming") }}</p>

<h2 id="概要">概要</h2>

<p><code><strong>PerformanceTiming</strong></code><strong><code>.requestStart</code></strong> 是一个返回代表一个时刻的 <code>unsigned long long</code> 型只读属性，为浏览器发送从服务器或者缓存获取实际文档的请求之时的 Unix毫秒时间戳。如果传输层在请求开始之后发生错误并且连接被重新打开，则该属性将会被设定为新的请求的相应的值 。</p>

<h2 id="语法">语法</h2>

<pre class="syntaxbox"><em>time</em> = <em>performanceTiming</em>.requestStart;</pre>

<h2 id="标准">标准</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('Navigation Timing', '#dom-performancetiming-requeststart', 'PerformanceTiming.requestStart')}}</td>
   <td>{{Spec2('Navigation Timing')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<div>
<div>


<p>{{Compat("api.PerformanceTiming.requestStart")}}</p>
</div>
</div>

<h2 id="参见">参见</h2>

<ul>
 <li>它属于 {{domxref("PerformanceTiming")}} 接口。</li>
</ul>