feat(Listenable): Implements Listenable class

modules/util/Listenable.js

@@ -0,0 +1,39 @@
+import EventEmitter from "events";
+
+/**
+ * The class implements basic event operations - add/remove listener.
+ * NOTE: The purpose of the class is to be extended in order to add
+ * this functionality to other classes.
+ */
+export default class Listenable {
+    /**
+     * Creates new instance.
+     * @param {EventEmitter} eventEmitter
+     * @constructor
+     */
+    constructor(eventEmitter = new EventEmitter()) {
+        this.eventEmitter = eventEmitter;
+        // aliases for addListener/removeListener
+        this.addEventListener = this.on = this.addListener;
+        this.removeEventListener = this.off = this.removeListener;
+    }
+
+    /**
+     * Adds new listener.
+     * @param {String} eventName the name of the event
+     * @param {Function} listener the listener.
+     */
+    addListener (eventName, listener) {
+        this.eventEmitter.addListener(eventName, listener);
+    }
+
+    /**
+     * Removes listener.
+     * @param {String} eventName the name of the event that triggers the
+     * listener
+     * @param {Function} listener the listener.
+     */
+    removeListener (eventName, listener) {
+        this.eventEmitter.removeListener(eventName, listener);
+    }
+}