Lazy Load youtube video from iframe API

 https://stackoverflow.com/questions/37856498/lazy-load-youtube-video-from-iframe-api

<div id="placeholder">
<img src="http://img.youtube.com/vi/M7lc1UVf-VE/sddefault.jpg" />
</div>
</div>
<div id="player"></div>

<script>

document.getElementById("placeholder").addEventListener("click", function(){
    this.style.display = 'none';
    loadYT()
});
  // 2. This code loads the IFrame Player API code asynchronously.
  function loadYT() {
    var tag = document.createElement('script');
    tag.src = "https://www.youtube.com/iframe_api";
    var firstScriptTag = document.getElementsByTagName('script')[0];
    firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);
  }

  // 3. This function creates an <iframe> (and YouTube player)
  //    after the API code downloads.
  var player;

  function onYouTubeIframeAPIReady() {
    player = new YT.Player('player', {
      height: '390',
      width: '640',
      videoId: 'M7lc1UVf-VE',
      events: {
        'onReady': onPlayerReady,
        'onStateChange': onPlayerStateChange
      }
    });
  }

  // 4. The API will call this function when the video player is ready.
  function onPlayerReady(event) {
    event.target.playVideo();
  }

  // 5. The API calls this function when the player's state changes.
  //    The function indicates that when playing a video (state=1),
  //    the player should play for six seconds and then stop.
  var done = false;

  function onPlayerStateChange(event) {
    if (event.data == YT.PlayerState.PLAYING && !done) {
      setTimeout(stopVideo, 6000);
      done = true;
    }
  }

  function stopVideo() {
    player.stopVideo();
  }

</script>