@adt/event-emitter/dist/EventEmitter.cjs.js

Simple event emmiter implementation

'use strict';

/**
 * Callback
 * @class
 * @private
 * @param {String} evtName Event name
 * @param {Function} callback Callback function
 * @param {Object} context Callback execution context
 * @param {?Object} args Additional arguments
 */
function Callback(evtName, callback, context, args) {

    return Object.freeze(Object.create(null, {
        evtName: { value: evtName },
        callback: { value: callback },
        context: { value: context },
        args: { value: args }
    }));
}

/**
 * EventEmitter
 */
function EventEmitter() {
    var _this = this;

    var callbacks = new Map();

    var ret = Object.create(EventEmitter.prototype, {

        /**
         * Register callback function.<br />
         * Event object will be passed to registered callback function as first argument.
         * @name EventEmitter#on
         * @memberof EventEmitter
         * @function
         * @param {String} evtName Event name
         * @param {Function} cbf Callback function
         * @param {Object} [context=EventEmitter] Callback execution context (this)
         */
        on: { value: function value(evtName, cbf, context) {

                var ctx = context || _this;

                var cb = Callback(evtName, cbf, ctx);

                if (callbacks.has(evtName)) {
                    callbacks.get(evtName).push(cb);
                } else {
                    callbacks.set(evtName, [cb]);
                }
            } },

        /**
         * Execute callbacks on given event if callbacks exist for this event (emit events).
         * @protected
         * @param {String} evtName Event name
         * @param {Object} evt Associated source event
         */
        emit: { value: function value(evtName, evt) {

                if (callbacks.has(evtName)) {

                    callbacks.get(evtName).forEach(function (cb) {
                        return cb.callback.call(cb.context, evt);
                    });
                }
            } }

    });

    return ret;
}

module.exports = EventEmitter;