JS: Lazy Load Youtube Videos

<script>
( function() {
    setTimeout( function() {
        var youtube = document.querySelectorAll( ".youtube" );

        for ( var i = 0; i < youtube.length; i++ ) {

            var source = "https://img.youtube.com/vi/" + youtube[ i ].dataset.embed + "/sddefault.jpg";

            var image = new Image();
            image.src = source;
            image.addEventListener( "load", function() {
                youtube[ i ].appendChild( image );
            }( i ) );

            youtube[ i ].addEventListener( "click", function() {

                var iframe = document.createElement( "iframe" );

                iframe.setAttribute( "frameborder", "0" );
                iframe.setAttribute( "allowfullscreen", "" );
                iframe.setAttribute( "src", "https://www.youtube.com/embed/" + this.dataset.embed + "?rel=0&showinfo=0&autoplay=1" );

                this.innerHTML = "";
                this.appendChild( iframe );
            } );
        };
    }, 100 );
} )();
</script>