How can i check if a JavaScript-Eventhandler has been set?

Question

I\'ve got a JavaScript-function that sets the \"onclick\"-event of some HTML-Nodes - even if that \"onclick\"-event has been set before.

How can i check if that ev

Answer 1

It should be possible to detect event handlers attached using .addEventListener() by intercepting calls to the function:

var myListOfAddedEvents = [];

var realAddEventListener = HTMLElement.prototype.addEventListener;

HTMLElement.prototype.addEventListener = function(evtType,fn,cap) {
    myListOfAddedEvents.push(
        {on: this, type: evtType, handler: fn, capture: cap}
    );

    return realAddEventListener.apply(this, arguments);
};

Note: That is untested code and may need some work. I'm hoping this same function will be used by all element types, but I could be wrong. Also it will only work if you can run this bit of code before they start adding events. A copy for attachEvent could be constructed similarly.