<html>
<body>
<video width="320" height="240" controls>
<source id="mySource" src="movie.mp4" type="video/mp4" media="screen and (min-width:320px)">
<source src="movie.ogg" type="video/ogg" media="screen and (min-width:320px)">
您的浏览器不支持 video 标签。
</source></source></video>
<p>点击按钮返回媒体资源的 media 属性的值。</p>
<p id="demo"></p>
<button onclick="myFunction()">尝试一下</button>
<script>
function myFunction()
{
var x = document.getElementById("mySource").media;
document.getElementById("demo").innerHTML = x;
};
</script>
</body>
</html>