A general purpose event dispatcher

Dispatcher.js

/** @constructor */
function Dispatcher(context, events) {
    this.ctx = context;
    this.events = events;
    this.listeners = {};
}

/**
 * Adds an event listener to an event
 *
 * @param {string} event the name of the event to be listened to
 * @param {function} fn the callback to fire when the event is emitted
 */
Dispatcher.prototype.addEventListener = function (event, fn) {
    if (this.events.indexOf(event) > -1) {
        if (!this.listeners.hasOwnProperty(event)) {
            this.listeners[event] = [];
        }
        this.listeners[event].push(fn);
    }
}

/**
 * Removes a previosly registered event listener from an event
 *
 * @param {string} event the name of the event
 * @param {function} fn the callback to be removed
 */
Dispatcher.prototype.removeEventListener = function (event, fn) {
    if (this.listeners.hasOwnProperty(event)) {
        this.listeners[event] = this.listeners[event].filter(function (listener) {
            return listener.toString() !== fn.toString();
        });
    }
}

/**
 * Emits an event
 *
 * @param {string} event the event to be emitted
 * @param {array} [args] arguments to pass to the callback
 */
Dispatcher.prototype.emit = function (event, args) {
    var dispatcher = this;

    if (this.listeners.hasOwnProperty(event)) {
        this.listeners[event].forEach(function (listener) {
            listener.apply(dispatcher.ctx, args);
        });
    }
}