Youtube Auto Subtitle For XianTiao Tech.js

function get_auto_subtitle_xml_url(){
    var raw_string = ytplayer.config.args.player_response;
    var json = JSON.parse(raw_string);
    var captionTracks = json.captions.playerCaptionsTracklistRenderer.captionTracks;
    for (var index in captionTracks){
        var caption = captionTracks[index];
        if(typeof caption.kind === 'string' && caption.kind == 'asr'){
            return captionTracks[index].baseUrl + "&fmt=3";
        }
        // ASR – A caption track generated using automatic speech recognition.
        // https://developers.google.com/youtube/v3/docs/captions
    }
    return null;
}