files/zh-cn/web/api/mediasource/readystate/index.html


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---
title: MediaSource.readyState
slug: Web/API/MediaSource/readyState
translation_of: Web/API/MediaSource/readyState
---
<div>{{APIRef("Media Source Extensions")}}{{SeeCompatTable}}</div>

<p><code><strong>readyState</strong></code>是 {{domxref("MediaSource")}} 接口的一个只读属性。它返回一个集合表明当前<code>MediaSource</code>的状态。它有三种可能的返回值：</p>

<ul>
 <li><code>closed</code>: 当前源并未附着到一个media元素上。</li>
 <li><code>open</code>: 当前源已附着到一个media元素并准备好接收 {{domxref("SourceBuffer")}} 对象。</li>
 <li><code>ended</code>: 当前源已附着到一个media元素，但流已被{{domxref("MediaSource.endOfStream()")}}结束。</li>
</ul>

<h2 id="语法">语法</h2>

<pre class="brush: js">var myReadyState = mediaSource.readyState;</pre>

<h3 id="值">值</h3>

<p>A {{domxref("DOMString")}}.</p>

<h2 id="例子">例子</h2>

<p>The following snippet is from a simple example written by Nick Desaulniers (<a href="http://nickdesaulniers.github.io/netfix/demo/bufferAll.html">view the full demo live</a>, or <a href="https://github.com/nickdesaulniers/netfix/blob/gh-pages/demo/bufferAll.html">download the source</a> for further investigation.)</p>

<pre class="brush: js  language-js"><code class="language-js"><span class="keyword token">if</span> <span class="punctuation token">(</span><span class="string token">'MediaSource'</span> <span class="keyword token">in</span> window <span class="operator token">&amp;&amp;</span> MediaSource<span class="punctuation token">.</span><span class="function token">isTypeSupported<span class="punctuation token">(</span></span>mimeCodec<span class="punctuation token">)</span><span class="punctuation token">)</span> <span class="punctuation token">{</span>
  <span class="keyword token">var</span> mediaSource <span class="operator token">=</span> <span class="keyword token">new</span> <span class="class-name token">MediaSource</span><span class="punctuation token">;</span>
 <span class="comment token"> //console.log(mediaSource.readyState); // closed
</span>  video<span class="punctuation token">.</span>src <span class="operator token">=</span> URL<span class="punctuation token">.</span><span class="function token">createObjectURL<span class="punctuation token">(</span></span>mediaSource<span class="punctuation token">)</span><span class="punctuation token">;</span>
  mediaSource<span class="punctuation token">.</span><span class="function token">addEventListener<span class="punctuation token">(</span></span><span class="string token">'sourceopen'</span><span class="punctuation token">,</span> sourceOpen<span class="punctuation token">)</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span> <span class="keyword token">else</span> <span class="punctuation token">{</span>
  console<span class="punctuation token">.</span><span class="function token">error<span class="punctuation token">(</span></span><span class="string token">'Unsupported MIME type or codec: '</span><span class="punctuation token">,</span> mimeCodec<span class="punctuation token">)</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span>

<span class="keyword token">function</span> sourceOpen <span class="punctuation token">(</span>_<span class="punctuation token">)</span> <span class="punctuation token">{</span>
 <span class="comment token"> //console.log(this.readyState); // open
</span>  <span class="keyword token">var</span> mediaSource <span class="operator token">=</span> <span class="keyword token">this</span><span class="punctuation token">;</span>
  <span class="keyword token">var</span> sourceBuffer <span class="operator token">=</span> mediaSource<span class="punctuation token">.</span><span class="function token">addSourceBuffer<span class="punctuation token">(</span></span>mimeCodec<span class="punctuation token">)</span><span class="punctuation token">;</span>
  <span class="function token">fetchAB<span class="punctuation token">(</span></span>assetURL<span class="punctuation token">,</span> <span class="keyword token">function</span> <span class="punctuation token">(</span>buf<span class="punctuation token">)</span> <span class="punctuation token">{</span>
    sourceBuffer<span class="punctuation token">.</span><span class="function token">addEventListener<span class="punctuation token">(</span></span><span class="string token">'updateend'</span><span class="punctuation token">,</span> <span class="keyword token">function</span> <span class="punctuation token">(</span>_<span class="punctuation token">)</span> <span class="punctuation token">{</span>
      mediaSource<span class="punctuation token">.</span><span class="function token">endOfStream<span class="punctuation token">(</span></span><span class="punctuation token">)</span><span class="punctuation token">;</span>
      video<span class="punctuation token">.</span><span class="function token">play<span class="punctuation token">(</span></span><span class="punctuation token">)</span><span class="punctuation token">;</span>
     <span class="comment token"> //console.log(mediaSource.readyState); // ended
</span>    <span class="punctuation token">}</span><span class="punctuation token">)</span><span class="punctuation token">;</span>
    sourceBuffer<span class="punctuation token">.</span><span class="function token">appendBuffer<span class="punctuation token">(</span></span>buf<span class="punctuation token">)</span><span class="punctuation token">;</span>
  <span class="punctuation token">}</span><span class="punctuation token">)</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span><span class="punctuation token">;</span></code></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('Media Source Extensions', '#widl-MediaSource-readyState', 'readyState')}}</td>
   <td>{{Spec2('Media Source Extensions')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性表格">浏览器兼容性表格</h2>

{{Compat("api.MediaSource.readyState")}}

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

<ul>
 <li>{{domxref("SourceBuffer")}}</li>
 <li>{{domxref("SourceBufferList")}}</li>
</ul>