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;      }    },  getEvent : function (event){      return event ? event : window.event;     },   preventDefault : function(event){      if(event.preventDefault){         event.preventDefault();      }else{         event.returnValue = false;      }   },  removeHandsler : 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] = handler;     }    }   stopPropagation : function(event){      if(event.stopPropagation){         event.stopPropagation();      }else {          event.cancelBubble = true;      }    },   getRelatedTarget : function(event){      if(event.relatedTarget){          return event.relatedTarget;      }else if (event.toElement){          return event.toElement;      }else if(event.fromElement){          return event.fromElement;      }esle {          return null;       }    },    getButton : function (event){       if(document.implementation.hasFeature("MouseEvents" , "2.0")){          return event.button;       }else{           switch(event.button){             case 0:             case 1:             case 3:             case 5:             case 7:               return 0;             case 2:             case 6:               return 2;             case 4:               return 1;            }        }     }} ;

var btn = document.getElementById("myBtn");var handler = function(){  alert("Clicked");};EventUtil.addHandler(btn , "click", handler);//略去其他代碼EventUtil.removeHandler(btn, "click", handler);