Lazy Load youtube video from iframe API

Question

I want to lazy load the youtube video with iframe API. ie. load only the poster image in the beginning and when user clicks on it then only load the actual image and its content.

Answer 1

Most of this is taken from the getting started section on the youtube page.

<!-- 1. The <iframe> (and video player) will replace this <div> tag. -->
    <div id="player"></div>

    <script>
      // 2. This code loads the IFrame Player API code asynchronously.
      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>

This example loads the video when it is ready.

So we change it up a bit to add in a placeholder image and on click hide the image and play the video.

Wrap the tag (step 2) in function

  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);
  }

Add an image Check this question for more details on sizes.

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

Then on click hide the placeholder image and load the player

document.getElementById("placeholder").addEventListener("click", function(){
    this.style.display = 'none';
    loadYT()
});

Final result can be seen below.

<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>