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

看完这一节，自己写了一个DOM二级事件函数，但老是报错：obj is null ！

<!DOCTYPE html>
<html>
<head>
   <meta charset="UTF-8">
   <title>Document</title>
   <script type="text/javascript">

        var btn = document.getElementById('btn');


       function show(){
           alert('事件监听');
        }

       var eventUntil = {
           //添加事件
           Add:function(obj,type,Event){
               if(obj.addEventListerner){     //兼容谷歌，火狐
                   obj.addEventListerner(type,Event,false);
               }
               else if(obj.attachEvent){    //兼容IE，Opera
                   obj.attachEvent('on'+type,Event);
               }
               else{
                   obj['on'+type] = Event;
               }
           },
           //删除事件
           Remove:function(obj,type,Event){
               if(obj.removeEventListerner){     //兼容谷歌，火狐
                   obj.removeEventListerner(type,Event,false);
               }
               else if(obj.detachEvent){    //兼容IE，Opera
                   obj.detachEvent('on'+type,Event);
               }
               else{
                   obj['on'+type] = null;
               }
           }

       }
       eventUntil.Add(btn,'click',show)
   </script>
</head>
<body>
   <input type="button" value="btn" id="btn"></input>
</body>
</html>