Youtube player with loop using Iframe API

loop.js

<script>
  // Inject this code
  var tag = document.createElement('script');

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

  var player;
  function onYouTubeIframeAPIReady() {
    player = new YT.Player('player', {
        videoId: 'WANTED_VIDEO_ID',
        events: {
          'onStateChange': onPlayerStateChange
        }
    });
  }

  function onPlayerStateChange(e) {
    if (e.data === YT.PlayerState.ENDED) {
      player.playVideo(); 
    }
  }
</script>