Mulitple Elements with the same ID

Id must be unique. You should use class instead and then make use of document.getElementsByClassName('className');

var video = document.getElementsByClassName('vid');
var myFunction = function() {
    // Reset the video to 
    this.currentTime = 0;
    // And play again
    this.load();
};

for (var i = 0; i < video.length; i++) {
    video[i].addEventListener('ended', myFunction, false);
}