Enumerate events/eventListeners for a WinJS object

I'm using pure WinJS for a project (No jQuery) and have run into a requirement that has me stumped.

Let's say I have a DOM element called 'bob' (although this might not necessarily be a DOM element). To attach an event listener, I would do this:

bob.addEventListener('click', function ()
{
  // Some code goes here
});

There is nothing stopping me from adding lots of event listeners to 'bob', even for the same event names (which is fine as they are just queued) - herein lies the rub!

I need to be able to enumerate the events/listeners that are attached to a given object so I can selectively replace or tweak some of them at runtime.

Any thoughts on how to acheive this?

Solution

It turns out that you can, in some circumstances, enumerate attached event listeners.

If you are using the 'Events' Mixin on an object, then once you have called one of the mixed-in methods (addEventListener, removeEventListener or dispatchEvent), your target object will gain a property called _listeners (assuming it doesn't already exist).

For a practical example, here's a function that counts the number of attached event listeners for an object that uses this mixin:

/*
 * Counts the number of attached listeners
 */
 countListeners: function()
 {
    var count = 0;

    if (this._listeners)
    {
       var key;

       for (key in this._listeners)
       {
          if (this._listeners.hasOwnProperty(key))
          {
             count++;
          }
       }
    }

    return count;
 }

Hope this helps someone!