Control HTML5 video player loop with JavaScript

You can detect if the loop property is supported, and set it to true.

For browsers that don't support it, you can simply bind the ended media event, and start it over:

var myVideo = document.getElementById('videoId');
if (typeof myVideo.loop == 'boolean') { // loop supported
  myVideo.loop = true;
} else { // loop property not supported
  myVideo.addEventListener('ended', function () {
    this.currentTime = 0;
    this.play();
  }, false);
}
//...
myVideo.play();