addEventListener and emit complete.

src/EventEmitter.js

@@ -0,0 +1,117 @@
+/*
+Event Emitter
+
+an event emitter is responsible for managing a set of listeners and publishing events to them when it is told such events happened
+used in async event driven architecture
+
+API:
+	addListener
+	removeListener
+	removeAllListeners
+	emit
+	once
+	listeners
+
+http://learnjswith.me/build-an-event-emitter-in-javascript/
+*/
+
+class Emitor {
+	constructor () {
+		this.events = {};
+	}
+
+	isValidEvent(eventName) {
+		const events = this.events;
+		return events.hasOwnProperty(eventName) && Array.isArray(events[eventName]);
+	}
+
+	/**
+		* Adds a listener to be invoked when events of the specified type are emitted.
+		*
+		* @param {string}   eventName    Name of the event to listen to
+		* @param {function} callback Function to invoke when the specified event is emitted
+  **/
+	addListener(eventName, callback) {
+	  const events = this.events;
+
+		if (typeof callback === 'function') {
+	    if (this.isValidEvent(eventName)) {
+	      events[eventName].push(callback);
+	    } else {
+	      events[eventName] = [callback];
+	    }
+	  }
+	}
+
+	/**
+		* Alias to addListener
+	**/
+  on(event, listener) {
+    this.addListener(event, listener);
+  }
+
+	/**
+   * Emits an event of the given type with the given data. All handlers of that particular type will be notified.
+   *
+   * @param {string} event Name of the event to emit
+   * @param {*}            Arbitrary arguments to be passed to each
+   *                       registered listener
+   *
+   * @example
+   *   emitter.addListener('someEvent', (message) => {
+   *     console.log(message)
+   *   })
+   *
+   *   emitter.emit('someEvent', 'hello') // logs 'hello'
+   */
+
+	emit(eventName,  ...args) {
+	  const events = this.events
+
+		if (this.isValidEvent(eventName)) {
+
+	    // create a shallow copy
+	    let listeners = [...events[eventName]];
+
+			listeners.forEach((listener) => {
+				if (listener) {
+	        listener.apply(this, args);
+	      }
+			});
+	  }
+	}
+
+	// removeListener(eventName) {
+	//   const events = this.events;
+	//   let listeners;
+	//   let listenerString;
+	//
+	//   if (
+	// 		typeof listener === 'function' &&
+	//     events.hasOwnProperty(event) &&
+	//     Array.isArray(events[event])
+	// 	) {
+	//     listeners = this.listeners(event);
+	//     listenerString = listener.toString();
+	//     for (let i = 0; i < listeners.length; i++) {
+	//       if (listeners[i].toString() === listenerString) {
+	//         listeners.splice(i, 1);
+	//       }
+	//     }
+	//   }
+	// }
+
+}
+
+
+const emitor = new Emitor();
+
+const callback1 = function(x, y) {console.log(x + y)}
+const callback2 = function(x, y) {console.log(y + x)}
+
+emitor.addListener('event_1', callback1);
+// emitor.addListener('event_1', callback2);
+
+console.log('emitor', emitor);
+
+emitor.emit('event_1', 'hello', ' world')