特写：兼容的事件处理函数工具包

var EventUtil = {             
    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" + type] = handler;       
       }   
    },           
    removeHandler: function(element, type, handler){      
       if (element.removeEventListener){         
           element.removeEventListener(type, handler, false);      
       } else if (element.detachEvent){         
           element.detachEvent("on" + type, handler);    
       } else {       
           element["on" + type] = null;    
       }    
    },  
    getEvent: function(event){     
        return event ? event : window.event;    
    },        
    getTarget: function(event){       
        return event.target || event.srcElement; 
    },        
    preventDefault: function(event){
       if (event.preventDefault){ 
           event.preventDefault();       
       } else {  
           event.returnValue = false;      
       }   
    },                    
    stopPropagation: function(event){      
      if (event.stopPropagation){        
         event.stopPropagation();     
      } else {         
         event.cancelBubble = true;     
      }    
    }         
};