YouTube Video Playing and Finished Event Handling

YouTubeEventHandling.js

let player
let onYouTubeIframeAPIReady

const youTubeReady = new Promise(resolve => {

var tag = document.createElement('script');
tag.src = "//www.youtube.com/iframe_api";
var firstScriptTag = document.getElementsByTagName('script')[0];
firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);

onYouTubeIframeAPIReady = resolve

})

youTubeReady.then(() =>{
    player = new YT.Player('player', {
        height: '254',
        width: '451',
        videoId: '{{ current_phase.video_id }}',
        events: {
            'onStateChange': onPlayerStateChange
        }
    });
})

function onPlayerReady(event) {
    event.target.playVideo();
}

function onPlayerStateChange(event) {
    if (event.data == YT.PlayerState.PLAYING) {
        _gaq.push(['_trackEvent', 'Video', 'Play']);
    }else if ( event.data == YT.PlayerState.ENDED){
        _gaq.push(['_trackEvent', 'Video', 'Finish']);
    }
}