
<!-- Example: addEvent(window, "load", "functionName", false);  -->
function addEvent(obj, evType, fn, useCapture){
    if (obj.addEventListener){
        obj.addEventListener(evType, fn, useCapture);
        return true;
    } else if (obj.attachEvent){
        return obj.attachEvent("on" + evType, fn);
    } else {
        alert('Event Handler could not be attached');
        return false;
    }
}

function removeEvent(obj, evType, fn, useCapture){
    if (obj.removeEventListener){
        obj.removeEventListener(evType, fn, useCapture);
        return true;
    } else if (obj.detachEvent){
        return obj.detachEvent("on" + evType, fn);
    } else {
        alert('Event Handler could not be removed');
        return false;
    }
}

<!-- Custom event handling/management - The following can be used to create custom javascript events. -->
function EventTarget(){
    this._listeners = {};
}

EventTarget.prototype = {

    constructor: EventTarget,

    addListener: function(type, listener){
        if (typeof this._listeners[type] == "undefined"){
            this._listeners[type] = [];
        }

        this._listeners[type].push(listener);
    },

    fire: function(event){
        if (typeof event == "string"){
            event = { type: event };
        }
        if (!event.target){
            event.target = this;
        }

        if (!event.type){  //false
            throw new Error("Event object missing 'type' property.");
        }

        if (this._listeners[event.type] instanceof Array){
            var listeners = this._listeners[event.type];
            for (var i=0, len=listeners.length; i < len; i++){
                listeners[i].call(this, event);
            }
        }
    },

    removeListener: function(type, listener){
        if (this._listeners[type] instanceof Array){
            var listeners = this._listeners[type];
            for (var i=0, len=listeners.length; i < len; i++){
                if (listeners[i] === listener){
                    listeners.splice(i, 1);
                    break;
                }
            }
        }
    }
};