Generic add/remove event functions for JavaScript

events.js

// Event handling functions modified from originals by Dean Edwards.
// http://dean.edwards.name/my/events.js

var guid = 1;

// Adds an event handler to the given element. The handler will be called
// in the context of the element with the event object as its only argument.
function addEvent(element, type, handler) {
    if (element.addEventListener) {
        element.addEventListener(type, handler, false);
    } else {
        if (element.nodeType === 3 || element.nodeType === 8) {
            return;
        }

        if (element.setInterval && (element !== window && !element.frameElement)) {
            element = window;
        }

        if (!handler.__guid) {
            handler.__guid = guid++;
        }

        if (!element.events) {
            element.events = {};
        }

        var handlers = element.events[type];
        if (!handlers) {
            handlers = element.events[type] = {};
            if (element["on" + type]) {
                handlers[0] = element["on" + type];
            }
        }

        handlers[handler.__guid] = handler;

        element["on" + type] = handleEvent;
    }
}

function handleEvent(event) {
    event = event || fixEvent(((this.ownerDocument || this.document || this).parentWindow || window).event);

    var result = true, handlers = this.events[event.type];

    for (var id in handlers) {
        if (handlers[id].call(this, event) === false) {
            result = false;
        }
    }

    return result;
}

function preventDefault() {
    this.returnValue = false;
}

function stopPropagation() {
    this.cancelBubble = true;
}

function fixEvent(event) {
    event.preventDefault = preventDefault;
    event.stopPropagation = stopPropagation;
    event.target = event.srcElement;
    event.keyCode = event.which;
    return event;
}

// Removes an event handler from the given element.
function removeEvent(element, type, handler) {
    if (element.removeEventListener) {
        element.removeEventListener(type, handler, false);
    } else {
        if (element.events && element.events[type] && handler.__guid) {
            delete element.events[type][handler.__guid];
        }
    }
}