MDL-63044 javascript: add simple pubsub implementation

lib/amd/build/pubsub.min.js

@@ -0,0 +1 @@
+define([],function(){var a={},b=function(b,c){a[b]=a[b]||[],a[b].push(c)},c=function(b,c){if(a[b])for(var d=0;d<a[b].length;d++)if(a[b][d]===c){a[b].splice(d,1);break}},d=function(b,c){a[b]&&a[b].forEach(function(a){a(c)})};return{subscribe:b,unsubscribe:c,publish:d}});

lib/amd/src/pubsub.js

@@ -0,0 +1,74 @@
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * A simple Javascript PubSub implementation.
+ *
+ * @module     core/pubsub
+ * @copyright  2018 Ryan Wyllie <[email protected]>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+define([], function() {
+
+    var events = {};
+
+    /**
+     * Subscribe to an event.
+     *
+     * @param {string} eventName The name of the event to subscribe to.
+     * @param {function} callback The callback function to run when eventName occurs.
+     */
+    var subscribe = function(eventName, callback) {
+        events[eventName] = events[eventName] || [];
+        events[eventName].push(callback);
+    };
+
+    /**
+     * Unsubscribe from an event.
+     *
+     * @param {string} eventName The name of the event to unsubscribe from.
+     * @param {function} callback The callback to unsubscribe.
+     */
+    var unsubscribe = function(eventName, callback) {
+        if (events[eventName]) {
+            for (var i = 0; i < events[eventName].length; i++) {
+                if (events[eventName][i] === callback) {
+                    events[eventName].splice(i, 1);
+                    break;
+                }
+            }
+        }
+    };
+
+    /**
+     * Publish an event to all subscribers.
+     *
+     * @param {string} eventName The name of the event to publish.
+     * @param {any} data The data to provide to the subscribed callbacks.
+     */
+    var publish = function(eventName, data) {
+        if (events[eventName]) {
+            events[eventName].forEach(function(callback) {
+                callback(data);
+            });
+        }
+    };
+
+    return {
+        subscribe: subscribe,
+        unsubscribe: unsubscribe,
+        publish: publish
+    };
+});