if you want to change the subtitles of other languages or add more subtitles, change the language tag of subtitles in line 36:'["en", "zh-CN"]'

核心代码如下：

    var myvideo = document.getElementsByTagName('video')[0];
for (var i = 0; i < myvideo.textTracks.length; i++) {
["en", "zh-CN"].indexOf(myvideo.textTracks[i].language) > -1 ? myvideo.textTracks[i].mode = "showing" : myvideo.textTracks[i].mode = "hidden";
}

不使用脚本或脚本失效时，只需在控制台执行以上代码，就能开启双字幕，但是每次切换视频都要重新执行一遍 核心代码是从别人的文章里看来的，来源