非常好的javascript：add event/ remove event

//------------------------------------
// heavily based on the Quirksmode addEvent contest winner, John Resig
// addEvent
function addEvent(obj,type,fn){
    if(obj.addEventListener) obj.addEventListener(type,fn,false);
    else if(obj.attachEvent){
        obj["e"+type+fn]=fn;
        obj[type+fn]=function(){obj["e"+type+fn](window.event);}
        obj.attachEvent("on"+type,obj[type+fn]);
    }
}

//------------------------------------
// removeEvent
function removeEvent(obj,type,fn){
  if(obj.removeEventListener) obj.removeEventListener(type,fn,false);
  else if(obj.detachEvent){
    obj.detachEvent("on"+type,obj[type+fn]);
    obj[type+fn]=null;
    obj["e"+type+fn]=null;
  }
}