https://www.alte-uni-mainz.de/fileadmin/templates2011/js/youtube.js

1( function() {
2
3    var youtube = document.querySelectorAll( ".youtube" );
4    
5    for (var i = 0; i < youtube.length; i++) {
6        
7        var source = "https://img.youtube.com/vi/"+ youtube[i].dataset.embed +"/sddefault.jpg";
8        
9        var image = new Image();
10                image.src = source;
11                image.addEventListener( "load", function() {
12                    youtube[ i ].appendChild( image );
13                }( i ) );
14        
15                youtube[i].addEventListener( "click", function() {
16
17                    var iframe = document.createElement( "iframe" );
18
19                            iframe.setAttribute( "frameborder", "0" );
20                            iframe.setAttribute( "allowfullscreen", "" );
21                            iframe.setAttribute( "src", "https://www.youtube.com/embed/"+ this.dataset.embed +"?rel=0&showinfo=0&autoplay=1" );
22
23                            //this.innerHTML = "";
24                            this.appendChild( iframe );
25                } );    
26    };
27    
28} )();