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---
title: MediaSource.duration
slug: Web/API/MediaSource/duration
translation_of: Web/API/MediaSource/duration
---
<div>{{APIRef("Media Source Extensions")}}{{SeeCompatTable}}</div>
<p>{{domxref("MediaSource")}} 接口的属性 <code><strong>duration</strong></code> 用来获取或者设置当前媒体展示的时长.</p>
<h2 id="语法">语法</h2>
<pre class="brush: js">mediaSource.duration = 5.5; // 5.5 seconds
var myDuration = mediaSource.duration;</pre>
<h3 id="值">值</h3>
<p>以秒为单位的 双精度浮点数.</p>
<h3 id="错误">错误</h3>
<p>设置新的值的时候可能会有下面的错误抛出.</p>
<table class="standard-table">
<thead>
<tr>
<th scope="col">错误</th>
<th scope="col">异常</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>InvalidAccessError</code></td>
<td>时长尝试设置一个负数, 或者 <code>NaN</code>.</td>
</tr>
<tr>
<td><code>InvalidStateError</code></td>
<td>{{domxref("MediaSource.readyState")}} 状态不是 <code>open</code>, 或者 一个或多个 {{domxref("SourceBuffer")}} 对象在 {{domxref("MediaSource.sourceBuffers")}} 中被更新 (例如. 该 {{domxref("SourceBuffer.updating")}}属性 为 <code>true</code>.)</td>
</tr>
</tbody>
</table>
<h2 id="例子">例子</h2>
<p>下面的代码片段取自 Nick Desaulniers写的简单例子 (想进一步了解 <a href="http://nickdesaulniers.github.io/netfix/demo/bufferAll.html">查看完整例子</a>, 或者 <a href="https://github.com/nickdesaulniers/netfix/blob/gh-pages/demo/bufferAll.html">下载源代码</a> .)</p>
<pre class="brush: js language-js"><code class="language-js"><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">;
mediaSource.duration = 120;</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-duration', 'duration')}}</td>
<td>{{Spec2('Media Source Extensions')}}</td>
<td>Initial definition.</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<div>
<p>{{Compat("api.MediaSource.duration")}}</p>
</div>
<h2 id="相关链接">相关链接</h2>
<ul>
<li>{{domxref("SourceBuffer")}}</li>
<li>{{domxref("SourceBufferList")}}</li>
</ul>
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