Cross browser event listener.

addEvent.js

function removeHandler(){
  this.element.removeEventListener(this.event, this.handler)
}

function detachHandler(){
  this.element.detachEvent('on' + this.event, this.handler)
}

function addEvent(ele, evt, fn){
  if(ele.addEventListener){
    function listenHandler(e){
      var ret = fn.apply(this, arguments);
      if(ret === false){
        e.stopPropagation();
        e.preventDefault();
      }
      return(ret);
    }

    ele.addEventListener(evt, listenHandler, false);
    return {
      element: ele,
      handler: listenHandler,
      event: evt,
      remove: removeHandler
    }
  } else {
    function attachHandler(){
      var ret = fn.call(ele, window.event);
      if(ret === false){
        window.event.returnValue = false;
        window.event.cancelBubble = true;
      }
      return(ret);
    }

    ele.attachEvent('on' + evt, attachHandler)
    return {
      element: ele,
      handler: attachHandler,
      event: evt,
      remove: detachHandler
    }
  }
}