オーディオタグの状態をモニターし、再生と一時停止します.

watchMusicState(){
     
        let _this = this;
        let $audio = document.getElementsByTagName('audio')[0];//    DOM  
        let playOrPause = document.getElementsByClassName('playOrPause')[0];
        // console.log($audio);
        $audio.addEventListener("playing", function(){
             //    Doing

            _this.playState = true;//    
                console.log(' ')
        });
        $audio.addEventListener("pause", function(){
      //    Doing

            
            _this.playState = false;//    
                console.log(' ')

        });
    }