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+---
+title: WebSocket.extensions
+slug: Web/API/WebSocket/extensions
+translation_of: Web/API/WebSocket/extensions
+---
+<p>{{APIRef("Web Sockets API")}}</p>
+
+<p><strong><code>WebSocket.extensions</code></strong>是只读属性，返回服务器已选择的扩展值。目前，链接可以协定的扩展值只有空字符串或者一个扩展列表。</p>
+
+<p>The <strong><code>WebSocket.extensions</code></strong> read-only property returns the extensions selected by the server. This is currently only the empty string or a list of extensions as negotiated by the connection.</p>
+
+<h2 id="语法">语法</h2>
+
+<pre class="syntaxbox"><em>var extensions</em> = aWebSocket.extensions;</pre>
+
+<h2 id="返回值">返回值</h2>
+
+<p>A {{domxref("DOMString")}}.</p>
+
+<h2 id="规范">规范</h2>
+
+<table class="standard-table">
+ <thead>
+  <tr>
+   <th scope="col">Specification</th>
+   <th scope="col">Status</th>
+   <th scope="col">Comment</th>
+  </tr>
+ </thead>
+ <tbody>
+  <tr>
+   <td>{{SpecName('HTML WHATWG', '#dom-websocket-extensions', 'WebSocket: extensions')}}</td>
+   <td>{{Spec2('HTML WHATWG')}}</td>
+   <td>Initial definition</td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="浏览器兼容性">浏览器兼容性</h2>
+
+
+
+<p>{{Compat("api.WebSocket.extensions")}}</p>