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<html>3
<head>4
<meta charset="utf-8">5
</head>6
<body>7
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<button onclick="getTextTracks()" type="button">获得可用文本轨道的数量</button>9
<br>10
<video id="video1" controls="controls">11
<source src="/examples/mov_bbb.mp4" type="video/mp4">12
<source src="/examples/mov_bbb.ogg" type="video/ogg">13
<track src="demo_sub.vtt">14
您的浏览器不支持 HTML5 video 标签。15
</video>16
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<script>18
myVid = document.getElementById("video1");19
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function getTextTracks() {21
alert(myVid.textTracks.length);22
}23
</script>24
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<p>Video courtesy of <a href="http://www.bigbuckbunny.org/" target="_blank">Big Buck Bunny</a>.</p>26
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</body>28
</html>