lfr-amd-loader/src/js/event-emitter.js

AMD Loader with support for combo URL and conditional loading

'use strict';

/**
 * Creates an instance of EventEmitter class.
 *
 * @constructor
 */

function EventEmitter() {
    this._events = {};
}

EventEmitter.prototype = {
    constructor: EventEmitter,

    /**
     * Adds event listener to an event.
     *
     * @param {string} event The name of the event.
     * @param {Function} callback Callback method to be invoked when event is being emitted.
     */
    on: function (event, callback) {
        var listeners = this._events[event] = this._events[event] || [];

        listeners.push(callback);
    },

    /**
     * Removes an event from the list of event listeners to some event.
     *
     * @param {string} event The name of the event.
     * @param {function} callback Callback method to be removed from the list of listeners.
     */
    off: function (event, callback) {
        var listeners = this._events[event];

        if (listeners) {
            var callbackIndex = listeners.indexOf(callback);

            if (callbackIndex > -1) {
                listeners.splice(callbackIndex, 1);
            } else {
                console.warn('Off: callback was not removed: ' + callback.toString());
            }
        } else {
            console.warn('Off: there are no listeners for event: ' + event);
        }
    },

    /**
     * Emits an event. The function calls all registered listeners in the order they have been added. The provided args
     * param will be passed to each listener of the event.
     *
     * @param {string} event The name of the event.
     * @param {object} args Object, which will be passed to the listener as only argument.
     */
    emit: function (event, args) {
        var listeners = this._events[event];

        if (listeners) {
            // Slicing is needed to prevent the following situation:
            // A listener is being invoked. During its execution, it may
            // remove itself from the list. In this case, for loop will
            // be damaged, since i will be out of sync.
            listeners = listeners.slice(0);

            for (var i = 0; i < listeners.length; i++) {
                var listener = listeners[i];

                listener.call(listener, args);
            }
        } else {
            console.warn('No listeners for event: ' + event);
        }
    }
};