JS does not work (SOLVED)

    var controler={
        openpic:function(x){        
            var pic=document.getElementById('picture'),           
            st=x.length, n=x.substr(2,st),
            im=new Image();
            im.onload=function(){                
                pic.appendChild(im);
            };            
            im.src='01.png';
        }
    };
    window.onload=function(){
        (function(){            
            var menu=document.getElementById('menu'),
            bt=menu.getElementsByTagName('option'),cbt=bt.length;
            for(var y=0;y<cbt;y++){
                bt[y].onclick=function(){                    
                    controler.openpic(this.id);
        };
    	}
        })();  

    };

<select name="ListBox" id="menu">
  <option id="bt1">img1</option>
  <option id="bt2">img2</option>
  </select>  

<div id="picture"></div>