---
title: EventSource.onopen
slug: Web/API/EventSource/open_event
tags:
  - API
  - Event Handler
  - EventSource
translation_of: Web/API/EventSource/onopen
original_slug: Web/API/EventSource/onopen
---
<div>{{APIRef('WebSockets API')}}</div>

<p>{{domxref("EventSource")}}接口的 <code><strong>onopen</strong></code> 属性是一个 {{event("Event_handlers", "event handler")}} ，它在收到{{event("open")}} 事件时被调用，在那时，连接刚被打开。</p>

<h2 id="语法">语法</h2>

<pre class="syntaxbox">eventSource.onopen = function</pre>

<h2 id="示例">示例</h2>

<pre class="brush: js">evtSource.onopen = function() {
  console.log("Connection to server opened.");
};</pre>

<div class="note">
<p><strong>注意</strong> ：你可以在 GitHub 上看到一个完整的示例— 请看 <a href="https://github.com/mdn/dom-examples/tree/master/server-sent-events">使用php的SSE(服务器发送事件)demo。</a></p>
</div>

<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('HTML WHATWG', "comms.html#handler-eventsource-onopen", "onopen")}}</td>
   <td>{{Spec2('HTML WHATWG')}}</td>
   <td>Initial definition</td>
  </tr>
 </tbody>
</table>

<ul>
</ul>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

{{Compat("api.EventSource.onopen")}}

<h2 id="相关链接">相关链接</h2>

<ul>
 <li>{{domxref("EventSource")}}</li>
</ul>