non-skippable-video-html5.js

(function keepVideoFromSkipping() {

  // modified from https://stackoverflow.com/a/39754847
  function modifyBehavior(video) {      
    var timeTracking = {
      watchedTime: 0,
      currentTime: 0
    };
    var lastUpdated = 'currentTime';

    video.addEventListener('timeupdate', function () {
      if (!video.seeking) {
        if (video.currentTime > timeTracking.watchedTime) {
          timeTracking.watchedTime = video.currentTime;
          lastUpdated = 'watchedTime';
        }
        //tracking time updated  after user rewinds
        else {
          timeTracking.currentTime = video.currentTime;
          lastUpdated = 'currentTime';
        }
      }
    });

    // prevent user from seeking
    video.addEventListener('seeking', function () {
      // guard against infinite recursion:
      // user seeks, seeking is fired, currentTime is modified, seeking is fired, current time is modified, ....
      var delta = video.currentTime - timeTracking.watchedTime;
      if (delta > 0) {
        video.pause();
        //play back from where the user started seeking after rewind or without rewind
        video.currentTime = timeTracking[lastUpdated];
        video.play();
      }
    });
  }

  var existCondition = setInterval(function() {
    var video = document.querySelector('.js-my-video');
    if (video) {
        clearInterval(existCondition);
        modifyBehavior(video);
    }
  }, 100);
})();