为什么只要检测支持的类型，为什么要用JavaScript添加多个文件？我建议改为检测***类型，然后设置 src 。

Why add multiple files with JavaScript when you can just detect the types supported? I would suggest instead detecting the best type then just setting the src.

var source= document.createElement('source');
if (audio.canPlayType('audio/mpeg;')) {
    source.type= 'audio/mpeg';
    source.src= 'audio/song.mp3';
} else {
    source.type= 'audio/ogg';
    source.src= 'audio/song.ogg';
}
audio.appendChild(source);

添加与文件类型一样多的支票。

Add as many checks as you have file types.