HTML: Video `autoplay` with `promise` and `muted` default

video-autoplay.html

<video id="ouazPromo" muted autoplay>
  <source src="https://www.ottawa.edu/OttawaU/media/OttawaSurprise/Video/OUAZPromo.mp4" type="video/mp4" />
  <source src="https://www.ottawa.edu/OttawaU/media/OttawaSurprise/Video/OUAZPromo.webm" type="video/webm" />
  <source src="https://www.ottawa.edu/OttawaU/media/OttawaSurprise/Video/OUAZPromo.ogv" type="video/ogg" />
</video>
<button id="unmuteButton" class="sr-only"></button>
 
<script>
  var promise = document.getElementById('ouazPromo').play();
 
  if (promise !== undefined) {
    promise.then(_ => {
      console.log('Autoplay started!');
    }).catch(error => {
      unmuteButton.addEventListener('click', function() {
        video.muted = false;
      });
    });
  }
</script>