<button onclick="getVolume()" type="button">音量是多少?</button>
<button onclick="setHalfVolume()" type="button">把音量设置为 0.2</button>
<button onclick="setFullVolume()" type="button">把音量设置为 1.0</button>
<video id="video1" controls="controls">
<source src="/example/html5/mov_bbb.mp4" type="video/mp4">
<source src="/example/html5/mov_bbb.ogg" type="video/ogg">
Your browser does not support HTML5 video.
myVid=document.getElementById("video1");