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

很困惑，检查了好几遍没看出问题呢？大神求救

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>跨浏览器问题</title>
</head>

<body>

<div id="box">
<input type="button" value="submit1" id="btn1">
<input type="button" value="submit2" id="btn2">

</div>
<script>
var btn1=document.getElementById('btn1');
var btn2=document.getElementById('btn2');
function showmess(){
   alert('you are my message');
   }
var eventUtil={
   addHandler:function(element,type,handler){
   //DOM2 处理程序的方法
   if(element.addEventListener){
       element.addEventListener(type,handler,false);
       }
       //IE 处理程序方法
   else if(element.attachEvent){
       element.attachEvent('on'+type,handler);
       }
       //DOM0处理事件程序判断
   else{
       element['on'+type]=handler;//触发handler操作
       }
   }
}

//删除句柄
removeHandler:function(element,type,handler){
   if(element.removeEventListener){
       element.removeEventListener(type,handler,false);
       }
       //IE事件处理程序
   else if(element.detachEvent){
       element.detachEvent('on'+type,handler);
       }
   else{
       element['on'+type]=null;
       }
   }
eventUtil.addHandler(btn2,'click',showmess);

</script>

</body>
</html>