improved-youtube-api-controls.js

// Some structure lifted from the official API docs.
// https://developers.google.com/youtube/iframe_api_reference#Loading_a_Video_Player

// 1. Prep elements.
newPlayer = document.createElement('div');
newPlayer.setAttribute('id', 'yttest');
newPlayer.style.filter = 'grayscale(1) brightness(0.5)';
newPlayer.style.transition = '1s';
document.querySelectorAll('.flex-layout-base')[0].appendChild(newPlayer);

// 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;
var playerState;
var playerStateReverse;
function onYouTubeIframeAPIReady() {
  playerState = YT.PlayerState;
  playerStateReverse = Object.keys(YT.PlayerState).reduceRight((accum, key, i) => {
    accum[playerState[key]] = key;
    return accum;
  }, {});
  player = new YT.Player('yttest', {
    height: '720',
    width: '1280',
    videoId: '2ZwQia4lkpI',
    playerVars: {rel: '0', showinfo: '0', modesbranding: '1'},
    events: {
      'onReady': onPlayerReady,
      'onStateChange': onPlayerStateChange
    }
  });
}

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

// 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) {
  console.log('state change', playerStateReverse[event.data], event.data);
  if (event.data === 1) {
    player.a.style.filter = 'grayscale(0) brightness(1)';
    console.log('state change', 'remove grayscale');
  }
  else {
    player.a.style.filter = 'grayscale(1) brightness(0.5)';
    console.log('state change', 'apply grayscale');
  }
}
function stopVideo() {
  console.log('stop video');
  player.stopVideo();
}