webgme-engine/src/common/EventDispatcher.js

WebGME server and Client API without a GUI

/*globals define*/
/*eslint-env node, browser*/

/**
 * @author rkereskenyi / https://github.com/rkereskenyi
 */

define([], function () {
    'use strict';

    var EventDispatcher = function () {
        this._eventList = {};
    };

    EventDispatcher.prototype = {
        _eventList: null,
        _getEvent: function (eventName, create) {
            // Check if Array of Event Handlers has been created
            if (!this._eventList[eventName]) {

                // Check if the calling method wants to create the Array
                // if not created. This reduces unneeded memory usage.
                if (!create) {
                    return null;
                }

                // Create the Array of Event Handlers
                this._eventList[eventName] = [];
                // new Array
            }

            // return the Array of Event Handlers already added
            return this._eventList[eventName];
        },
        addEventListener: function (eventName, handler) {
            // Get the Array of Event Handlers
            var evt = this._getEvent(eventName, true);

            // Add the new Event Handler to the Array
            evt.push(handler);
        },
        removeEventListener: function (eventName, handler) {
            // Get the Array of Event Handlers
            var evt = this._getEvent(eventName);

            if (!evt) {
                return;
            }

            // Helper Method - an Array.indexOf equivalent
            var getArrayIndex = function (array, item) {
                for (var i = 0; i < array.length; i++) {
                    if (array[i] === item) {
                        return i;
                    }
                }
                return -1;
            };

            // Get the Array index of the Event Handler
            var index = getArrayIndex(evt, handler);

            if (index > -1) {
                // Remove Event Handler from Array
                evt.splice(index, 1);
            }
        },
        removeAllEventListeners: function (eventName) {
            // Get the Array of Event Handlers
            var evt = this._getEvent(eventName);

            if (!evt) {
                return;
            }

            evt.splice(0, evt.length);
        },
        dispatchEvent: function (eventName, eventArgs) {
            // Get a function that will call all the Event Handlers internally
            var handler = this._getEventHandler(eventName);
            if (handler) {
                // call the handler function
                // Pass in "sender" and "eventArgs" parameters
                handler(this, eventArgs);
            }
        },
        clearAllEvents: function () {
            this._eventList = {};
        },
        _getEventHandler: function (eventName) {
            // Get Event Handler Array for this Event
            var evt = this._getEvent(eventName, false);
            if (!evt || evt.length === 0) {
                return null;
            }

            // Create the Handler method that will use currying to
            // call all the Events Handlers internally
            var h = function (sender, args) {
                for (var i = 0; i < evt.length; i++) {
                    evt[i](sender, args);
                }
            };

            // Return this new Handler method
            return h;
        }
    };

    return EventDispatcher;
});