EventManager v1.0.1, an easy custom event manager for javascript

EventManager.js

/* EventManager, v1.0.1
*
* Copyright (c) 2009, Howard Rauscher
* Licensed under the MIT License
*/
 
(function() {
    
    function EventManager() {
        this._listeners = {};
    }
    EventManager.prototype = {
        addListener : function(name, fn) {
            (this._listeners[name] = this._listeners[name] || []).push(fn);
            return this;
        },
        removeListener : function(name, fn) {
            if(arguments.length === 1) { // remove all
                this._listeners[name] = [];
            }
            else if(typeof(fn) === 'function') {
                var listeners = this._listeners[name];
                if(listeners !== undefined) {
                    var foundAt = -1;
                    for(var i = 0, len = listeners.length; i < len && foundAt === -1; i++) {
                        if(listeners[i] === fn) {
                            foundAt = i;
                        }
                    }
                    
                    if(foundAt >= 0) {
                        listeners.splice(foundAt, 1);
                    }
                }
            }
 
            return this;
        },
        fire : function(name, args) {
            var listeners = this._listeners[name];
            args = args || [];
            if(listeners !== undefined) {
                var data = {}, evt;
                for(var i = 0, len = listeners.length; i < len; i++) {
                    evt = new EventManager.EventArg(name, data);
                    
                    listeners[i].apply(window, args.concat(evt));
                    
                    data = evt.data;
                    if(evt.removed) {
                        listeners.splice(i, 1);
                        len = listeners.length;
                        --i;
                    }
                    if(evt.cancelled) {
                        break;
                    }
                }
            }
            return this;
        },
        hasListeners : function(name) {
            return (this._listeners[name] === undefined ? 0 : this._listeners[name].length) > 0;
        }
    };
    EventManager.eventify = function(object, manager) {
        var methods = EventManager.eventify.methods;
        manager = manager || new EventManager();
        
        for(var i = 0, len = methods.length; i < len; i++) (function(method) {
            object[method] = function() {
                return manager[method].apply(manager, arguments);
            };
        })(methods[i]);
 
        return manager;
    };
    EventManager.eventify.methods = ['addListener', 'removeListener', 'fire'];
    
    EventManager.EventArg = function(name, data) {
        this.name = name;
        this.data = data;
        this.cancelled = false;
        this.removed = false;
    };
    EventManager.EventArg.prototype = {
        cancel : function() {
            this.cancelled = true;
        },
        remove : function() {
            this.removed = true;
        }
    };
    
    window.EventManager = EventManager;
})();

examples.js

/* EventManager Examples
 */
 
// remember to include EventManger source
 

/*
 * Create a simple event manager 
 */

// basic

    var manager = new EventManager();
    manager.addListener('myEventName', function() {
        alert('event thrown');
    });
    manager.fire('myEventName');


// pass parameters to event listeners

    manager.addListener('myEventWithArguments', function(number) {
        alert('the number is '+number);
    });
    
    var random = Math.random();
    manager.fire('myEventWithArguments', [random]);

/*
 * Use EventManager event instace to give your listeners more control
 */ 

// cancel event

    manager.addListener('myCancelledEvent', function(e) {
        e.cancel();
        
        alert('this will be fired');
    });
    manager.addListener('myCancelledEvent', function(e) {
        alert('this one will not');
    });
    
    manager.fire('myCancelledEvent');

// remove a listener from within a listener

    manager.addListener('myRemovedEvent', function(e) {
        alert('event fired');
        e.remove();
    });

    //alert will happen
    manager.fire('myRemovedEvent');
    
    // nothing will happen
    manager.fire('myRemovedEvent');


/*
 * Let your own classes accept event handlers
 */
 
    function Person(name) {
        this.name = name;
        EventManager.eventify(this);
    }
    Person.prototype.changeName = function(name) {
        this.name = name;
        
        this.fire('namechanged', [name]);
    }
    
    var instance = new MyClass();
    instance.addListener('namechanged', function(name) {
        alert('name changed to '+name);
    });
    instance.changeName('Howard');

At the end of the examples.js, on the line var instance = new MyClass();: I believe MyClass was gonna be Person

its very complex, please see this project https://github.com/uxitten/jetemit