Event Handling

When doing Ajax event handling is necessary. Most (or actually all) Ajax libraries support browser-abstracted event handling. I took from many of these and made my own with nice features from all of them.

I will list the features here later, but here's the code now:

////////////  EVENT  ///////////////
 
var addEvent;
var removeEvent;
var getEvent;
 
(function() {
    var curId = 0;
    var delayedListeners = [];
    var listeners = {};
    var windowLoaded = false;
    
    function getObjId(object) {
        if (!object.__eventId)
            object.__eventId = ++curId;
        return object.__eventId;
    }
    
    function getEventId(element, event, listener) {
        var listener = listener.length == 2 ? getObjId(listener[0]) + '_' + getObjId(listener[1]) : getObjId(listener);
        return getObjId(element) + "_" + event + "_" + listener;
    }
    
    function addListener(element, event, listener) {
        if (typeof element == 'string' && !windowLoaded) {
            delayedListeners.push(arguments);
            return true;
        }
        
        if (typeof element == "string")
            element = document.getElementById(element);
        if (!element)
            return false;
        var obj = listener.length == 2 ? listener[0] : element;
        var func = listener.length == 2 ? listener[1] : listener;
        
        var args = Array.prototype.splice.call(arguments, 3, arguments.length);
        var proxy = function(event) {
            args.push(event);
            func.apply(obj, args);
        }
        listeners[getEventId(element, event, listener)] = {listener: listener, proxy: proxy};
        
        if (element.addEventListener)
            element.addEventListener(event, proxy, false);
        else if (element.attachEvent)
            element.attachEvent('on' + event, proxy);
        
        return true;
    }
    
    function removeListener(element, event, listener) {
        if (typeof element == "string")
            element = document.getElementById(element);
        var eventId = getEventId(element, event, listener);
        if (!eventId in listeners)
            return false
        
        var proxy = listeners[eventId].proxy;
        delete listeners[eventId];
        
        if (element.removeEventListener)
            element.removeEventListener(event, proxy, false);
        else if (element.detachEvent)
            element.detachEvent('on' + event, proxy);
        return true;
    }
    
    addEvent = function(element, event, listener) {
        if (element.length && typeof element != 'string') {
            var args = Array.prototype.splice.call(arguments, 0, arguments.length);
            for (var i = 0; i < element.length; i++) {
                args[0] = element[i];
                addListener.apply(this, args);
            }
        } else
            addListener.apply(this, arguments);
    };
    
    removeEvent = function(element, event, listener) {
        if (element.length && typeof element != 'string') {
            for (var i = 0; i < element.length; i++)
                removeListener(element, event, listener);
        } else
            removeListener(element, event, listener);
    };
    
    function stop() {
        this.stopPropagation();
        this.preventDefault();
    }
    
    function find(nodeName, useRelatedTarget) {
        nodeName = nodeName.toUpperCase();
        var node = useRelatedTarget ? this.relatedTarget : this.target;
        while (node.nodeName != nodeName && node.parentNode)
            node = node.parentNode;
        if (node.nodeName == nodeName)
            return node;
    }
    
    getEvent = function(event, property) {
        if (event.isSetup)
            return event;
        
        if (isIE) {
            event = window.event;
            event.stopPropagation = new Function("this.cancelBubble = true");
            event.preventDefault = new Function("this.returnValue = false");
            event.target = event.srcElement;
            if ("fromElement" in event)
                event.relatedTarget = event.fromElement;
            else if ("toElement" in event)
                event.relatedTarget =  event.toElement;
            if (!("layerX" in event) && "offsetX" in event) {
                event.layerX = event.offsetX;
                event.layerY = event.offsetY;
            }
        } else {
            if (event.target.nodeType == 3) event.target = event.target.parentNode;
        }
        
        if ("button" in event)
            event.mouseButton = event.button != 2 ? 1 : 2;
        
        if (!("pageX" in event) && "clientX" in event) {
            event.pageX = event.clientX + (document.documentElement.scrollLeft || document.body.scrollLeft);
            event.pageY = event.clientY + (document.documentElement.scrollTop || document.body.scrollTop);
        }
        event.stop = stop;
        event.find = find;
        event.isSetup = true;
        return event;
    };
    
    function onWindowUnload() {
        if (!listeners) return;
        for (var i = 0; i < listeners.length; i++) {
            var element = listeners[i][0];
            var event = listeners[i][1];
            var proxy = listeners[i][4];
            try { // if the element no longer exists, don't throw an error
                if (element.removeEventListener)
                    element.removeEventListener(event, proxy, false);
                else if (element.detachEvent)
                    element.detachEvent('on' + event, proxy);
            } catch(e) {}
            delete listeners[i];
        }
        delete listeners;
    }
    
    function onWindowLoad() {
        windowLoaded = true;
        for (var i = 0; i < delayedListeners.length; i++) {
            addListener.apply(this, delayedListeners[i]);
        }
    }
    
    addEvent(window, 'unload', onWindowUnload);
    addEvent(window, 'load', onWindowLoad);
})();