<h3>演示如何访问 SOURCE 元素</h3>
<source id="mySource" src="/img/horse.mp3" type="audio/mpeg">
<source src="/img/horse.ogg" type="audio/ogg">
Your browser does not support the audio element.
<button onclick="myFunction()">试一下</button>
var x = document.getElementById("mySource").src;
document.getElementById("demo").innerHTML = x;