Event Debugging Shim - allows limiting and skipping of event listeners as well as inspection of attached listeners

event-debugger.js

(function () {
    // Limit the number of events to be attached
    var limits = {
        'keydown': 100
    };

    // Skip this number of events
    var skips = {
        'keydown': 1
    }

    var addEventListenerFunc = function(type, handler, useCapture) {
        if (!this.__eventListeners[type]) {
            this.__eventListeners[type] = [];
            this.__skippedListeners[type] = 0;
        }

        // die if the limits are reached for this type
        if (this.__eventListeners[type].length >= limits[type]) {
            return;
        }

        // die if the skipping this type
        if (this.__skippedListeners[type] < skips[type]) {
            this.__skippedListeners[type]++;
            return;
        }

        this.__eventListeners[type].push(handler.toString());
        return this._addEventListener.apply(this, arguments);
    };

    var getEventListenerFunc = function(type) {
        return this.__eventListeners[type];
    };

    // setup the DOM and window objects
    var attachTo = [0, HTMLDocument, Element, window];
    for (var i in attachTo) {
        if (!attachTo[i].prototype) {
            continue;
        }
        attachTo[i].prototype._addEventListener = attachTo[i].prototype.addEventListener;
        attachTo[i].prototype.addEventListener = addEventListenerFunc;
        attachTo[i].prototype.getEventListener = getEventListenerFunc;
        attachTo[i].prototype.__eventListeners = {};
        attachTo[i].prototype.__skippedListeners = {};
    }
})();