Try it Yourself - JavaScript Reference video

<!DOCTYPE html>
<html>
<body>

<p>Click the button to create a VIDEO element with controls that will play a movie in a .mp3 or .ogg file format (depending on browser support).</p>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
   var x = document.createElement("VIDEO");

   if (x.canPlayType("video/mp4")) {
   x.setAttribute("src","movie.mp4");
   } else {
   x.setAttribute("src","movie.ogg");
   }

   x.setAttribute("width", "320");
   x.setAttribute("height", "240");
   x.setAttribute("controls", "controls");
   document.body.appendChild(x);
}
</script>

</body>
</html>