W3School TIY
编辑您的代码：
<!DOCTYPE html> <html> <body> <button onclick="getAudioTracks()" type="button">获得可用音轨的数量</button> <br /> <br /> <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. </video> <script> myVid=document.getElementById("video1"); function getAudioTracks() { alert(myVid.audioTracks.length); } </script> </body> </html>
查看结果: