                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /DOM事件探秘

能不能帮我看一下哪里错了，谢谢

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>事件流</title>
</head>
<body>
<div>
    <input type="button" value="按钮" id="btn">
</div>
<script type="text/javascript">
    function shoeMes(){
       alert('hello world!');
   }
   var btn=document.getElementById('btn');
/*    btn.onclick=function(){
      alert('这是通过DOM0级添加的事件！');
   } */
   var eventUtil={
      //添加句柄
      addHandler:function(element,type,handler){
        if(element.addEventListener){
          element.addEventListener(type,handler,false);
       }else if(element.attachEvent){
          element.attachEvent('on'+type,handler);
       }else{
          element['on'+click]=handler;
       }
      },
      //删除句柄
      removeHandler:function(element,type,handler){
        if(element.addEventListener){
          element.removeEventListener(type,handler,false);
       }else if(element.attachEvent){
          element.detachEvent('on'+type,handler);
       }else{
          element['on'+click]=null;
       }
      }
   }
   eventUtil.addHandler(btn,'click',showMes);
</script>
</body>
</html>