为何这么写会报错!

错误在注释的地方
<body>
<script>
function create(elm,parent,fn){var element = document.createElement(elm);parent.appendChild(element);if(fn)fn(element);};
 var Class = function(properties){
   var _class = function(){return (arguments[0] !== null && this.initialize && typeof(this.initialize) == 'function') ? this.initialize.apply(this, arguments) : this;};
   _class.prototype = properties;
   return _class;
 }; 
 var ss = new Class({
 initialize:function(data){
this.data     = data;
for(var i=0; i<this.data.length;i++)  
{
   create('img',document.body,function(elm){
   elm.id = this.data[i].id; //========
   elm.className= this.data[i].className;//=========
   elm.src= this.data[i].src; //========this.data 不存在
   })
}
 }
 })
 var arr = [{id:'img1',className:'ss1',src:'http://comic.qq.com/images/comic/2005/10/31/yh/s/42.jpg'},{id:'img2',className:'ss2',src:'http://comic.qq.com/images/comic/2005/10/31/yh/s/63.jpg'},{id:'img3',className:'ss3',src:'http://comic.qq.com/images/comic/2005/10/31/yh/s/77.jpg'},{id:'img4',className:'ss4',src:'http://comic.qq.com/images/comic/2005/10/31/yh/s/13.jpg'},{id:'img5',className:'ss5',src:'http://comic.qq.com/images/comic/2005/10/31/yh/s/25.jpg'}];
var a = new ss(arr);
</script>
</body>
这是为什么呀?