Revision 927787 of EventSource

<p>{{APIRef("Websockets API")}}</p>

<p>The <strong><code>EventSource</code></strong> interface is used to receive server-sent events. It connects to a server over HTTP and receives events in <code>text/event-stream</code> format without closing the connection.</p>

<p><span style="line-height:1.5">You can set the <code>onmessage</code> attribute to a JavaScript function to receive non-typed messages (that is, messages with no </span><code style="font-size: 14px;">event</code><span style="line-height:1.5"> field). You can also call </span><code style="font-size: 14px;">addEventListener()</code><span style="line-height:1.5"> to listen for events just like any other <code><a href="/en-US/docs/Web/API/EventTarget">EventTarget</a></code>.</span></p>

<p>See <a href="/en/Server-sent_events/Using_server-sent_events" title="en/Server-sent events/Using server-sent events">Using server-sent events</a> for further details.</p>

<h2 id="Method_overview" name="Method_overview">Methods</h2>

<dl>
 <dt>{{domxref("EventSource.close()")}}</dt>
 <dd>Closes the connection, if any, and sets the <code>readyState</code> attribute to <code>CLOSED</code>. If the connection is already closed, the method does nothing.</dd>
</dl>

<h2 id="Attributes" name="Attributes">Properties</h2>

<dl>
 <dt>{{domxref("EventSource.onerror")}}</dt>
 <dd>Is an {{domxref("EventHandler")}} being called when an error occurs and the {{event("error")}} event is dispatched on this object.</dd>
 <dt>{{domxref("EventSource.onmessage")}}</dt>
 <dd>Is an {{domxref("EventHandler")}} being called when a {{event("message")}} event is received, that is when a message is coming from the source.</dd>
 <dt>{{domxref("EventSource.onopen")}}</dt>
 <dd>Is an {{domxref("EventHandler")}} being called when an {{event("open")}} event is received, that is when the connection was just opened.</dd>
 <dt>{{domxref("EventSource.readyState")}} {{readonlyinline}}</dt>
 <dd>An <code>unsigned short</code> representing the state of the connection. Possible values are <code>CONNECTING</code> (<code>0</code>), <code>OPEN</code> (<code>1</code>), or <code>CLOSED</code> (<code>2</code>).</dd>
 <dt>{{domxref("EventSource.url")}} {{readonlyinline}}</dt>
 <dd>A {{domxref("DOMString")}} representing the URL of the source.</dd>
</dl>

<p>&nbsp;</p>

<h2 id="See_also" name="See_also">Specifications</h2>

<p>&nbsp;</p>

<p>{{ spec("https://html.spec.whatwg.org/multipage/comms.html#the-eventsource-interface","Server-Sent Events: The EventSource Interface","CR") }}</p>

<ul>
</ul>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<p>{{ CompatibilityTable() }}</p>

<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</th>
  </tr>
  <tr>
   <td>&nbsp;Basic support</td>
   <td>9</td>
   <td>{{ CompatGeckoDesktop("6.0") }}</td>
   <td>{{ CompatUnknown() }}</td>
   <td>11</td>
   <td>5</td>
  </tr>
  <tr>
   <td>CORS&nbsp;support</td>
   <td>26</td>
   <td>{{ CompatGeckoDesktop("11.0") }}</td>
   <td>{{ CompatUnknown() }}</td>
   <td>12</td>
   <td>{{ CompatUnknown() }}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{ CompatAndroid("4.4") }}</td>
   <td>{{ CompatUnknown() }}</td>
   <td>{{CompatUnknown()}}</td>
   <td>{{ CompatUnknown() }}</td>
   <td>{{ CompatUnknown() }}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="See_also" name="See_also">See also</h2>

<ul>
 <li><a href="/en/Server-sent_events/Using_server-sent_events" title="en/Server-sent events/Using server-sent events">Using server-sent events</a></li>
</ul>