---
title: XMLHttpRequestEventTarget.onerror
slug: Web/API/XMLHttpRequestEventTarget/onerror
tags:
  - API
  - Event Handler
  - XMLHttpRequestEventTarget
translation_of: Web/API/XMLHttpRequestEventTarget/onerror
---
<div>{{APIRef("XMLHttpRequest")}}</div>

<p><strong><code>XMLHttpRequestEventTarget.onerror</code></strong> 是{{domxref("XMLHttpRequest")}} 事务由于错误而失败时调用的函数。</p>

<p>请注意只有在网络层级出现错误时才会调用此函数。如果错误只出现在应用层（比如发送一个HTTP的错误码），这个方法将不会被调用。</p>

<h2 id="Syntax" name="Syntax">语法</h2>

<pre class="syntaxbox"><em>XMLHttpRequest</em>.onerror = <em>callback</em>;</pre>

<h3 id="Values">Values</h3>

<ul>
 <li><code><em>callback</em></code> 是当请求失败时执行的函数。</li>
</ul>

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

<pre class="brush: js">var xmlhttp = new XMLHttpRequest(),
  method = 'GET',
  url = 'https://developer.mozilla.org/';

xmlhttp.open(<em>method</em>, <em>url</em>, true);
xmlhttp.onerror = function () {
  console.log("** An error occurred during the transaction");
};
xmlhttp.send();
</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('XMLHttpRequest', '#handler-xhr-onerror')}}</td>
   <td>{{Spec2('XMLHttpRequest')}}</td>
   <td>WHATWG living standard</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>



<p>{{Compat("api.XMLHttpRequestEventTarget.onerror")}}</p>