Draggable div with className

[admin]

I found this script by theZillion (<a href="http://thezillion.wordpress.com/2012/08/29/javascript-draggable-no-jquery/" rel="nofollow">http://thezillion.wordpress.com/2012/08/29/javascript-draggable-no-jquery/</a>) that makes a div draggable. I'm trying to use this script to move a div by class name. And not by ID.

I have an event handler that works, but not when I'm adding the script... The console shows no errors either. Any ideas about how to make this work?

This is the code I have:

function wrappmover(){
    var moveEvent = "dice-window-wrapper";
    var addClassArr= document.getElementsByClassName(moveEvent);
    for(var i=0; i<addClassArr.length; i++){
        var addClass = addClassArr[i];
        addClass.addEventListener("click", movewrapp, true);
    }       
    function movewrapp() {
        var classToMove = "dice-window-wrapper";
        var elems = document.getElementsByClassName(classToMove);
        var tzdragg = function(){
            return {
                 startMoving : function(evt){ 
                     evt = evt || window.event;
                     var posX = evt.clientX, 
                     posY = evt.clientY, 
                     a = document.getElementsByClassName(classToMove),
                     divTop = a.style.top,
                     divLeft = a.style.left;
                     divTop = divTop.replace('px','');
                     divLeft = divLeft.replace('px','');
                     var diffX = posX - divLeft, 
                     diffY = posY - divTop; 
                     document.onmousemove = function(evt){ 
                         evt = evt || window.event;
                         var posX = evt.clientX,
                         posY = evt.clientY, 
                         aX = posX - diffX,
                         aY = posY - diffY; 
                         tzdragg.move('elem',aX,aY);
                     }
                 },
                 stopMoving : function(){ 
                    document.onmousemove = function(){}
                 },
                 move : function(divid,xpos,ypos){ 
                     var a = document.getElementById(divid);
                     document.getElementById(divid).style.left = xpos + 'px';
                     document.getElementById(divid).style.top = ypos + 'px';
                 }
            }
        }();