Without jQuery:
if the listeners were added using elem.addEventListener() method, it is not easy to list these listeners. You can override the EventTarget.addEventListener() method by wrapping it with your own. Then you will have the information, what listeners were registered.
var f = EventTarget.prototype.addEventListener; // store original
EventTarget.prototype.addEventListener = function(type, fn, capture) {
this.f = f;
this.f(type, fn, capture); // call original method
alert('Added Event Listener: on' + type);
}
Working example you can find at http://jsfiddle.net/tomas1000r/RDW7F/
