iterator almost implemented.

src/EventEmitter.js

@@ -92,10 +92,10 @@ class Emitter {
 
 	  if (this.isValidEvent(eventName)) {
 			const callbacks = events[eventName];
-	    const stringifedCallback = callback.toString();
+	    const stringifedTargetCallback = callback.toString();
 
 			callbacks.forEach((callback, idx) => {
-				if (callback.toString() === stringifedCallback) {
+				if (callback.toString() === stringifedTargetCallback) {
 					events[eventName].splice(idx, 1);
 				}
 			});
@@ -118,8 +118,7 @@ class Emitter {
 		* Much like addListener, except the listener is removed after being invoked.
 		*
 		* @param {string}   eventName    Name of the event to listen to
-		* @param {function} listener Function to invoke only once when the given
-		*                            event is emitted
+		* @param {function} listener Function to invoke only once when the given event is emitted
 	*/
   once(eventName, callback) {
     const emitter = this;
@@ -139,7 +138,9 @@ class Emitter {
 		* @return {array}
 	*/
   listeners(eventName) {
-    return this.events.hasOwnProperty(eventName) ? this.events[eventName] : []
+    return this.events.hasOwnProperty(eventName)
+			? this.events[eventName]
+			: []
   }
 
 }

src/Iterator.js

@@ -1,10 +1,73 @@
 /*
 	Implement an Iterator of Iterators which traverses through  an arbitrary number of iterators. IE, an iterator which iterates over three list iterators in the following way:
-	
+
 	L1 = a1, a2, a3
 	L2 = b1, b2, b3
 	L3 = c1, c2, c3
 
 	Then the iterator should process them in this order:
 	a1, b1, c1, a2, b2, c2, a3, b3, c3
 */
+
+class IteratorFlattener {
+	constructor (interlist) {
+		this.interqueue = [];
+
+		for (let iterator of interlist) {
+			this.interqueue.push(iterator);
+		}
+	}
+
+	next () {
+		if (!this.hasNext()) {
+			throw new Error('No such element')
+		}
+		const iterator = this.interqueue.shift();
+		const val = iterator.next().value;
+		if (this.hasNext()) {
+			this.interqueue.push(iterator);
+		}
+		return val
+	}
+
+	hasNext (iterator) {
+		return this.interqueue.length !== 0;
+	}
+
+}
+
+const arr1 = ['a1', 'a2', 'a3', 'a4'];
+const arr2 = ['b1', 'b2', 'b3'];
+const arr3 = ['c1', 'c2', 'c3', 'c4'];
+
+const iterator1 = arr1[Symbol.iterator]();
+const iterator2 = arr2[Symbol.iterator]();
+const iterator3 = arr3[Symbol.iterator]();
+
+const iterators = [iterator1, iterator2, iterator3];
+const interList = iterators[Symbol.iterator]();
+
+const iteratorFlattener = new IteratorFlattener(interList);
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // a1
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // b1
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // c1
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // a2
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // b2
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // c2
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // a3
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // b3
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // c3
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // a3
+console.log('iteratorFlattener.next()', iteratorFlattener.next()); // a3
+
+
+// const array = ['a', 'b', 'c', 'd', 'e'];
+// const iterator = array[Symbol.iterator]();
+// const first = iterator.next().value
+// console.log('first', first);
+// console.log('iterator.next().value', iterator.next().value); // Since it was skipped, so it's not assigned
+// const third = iterator.next().value
+// console.log('third', third);
+// console.log('iterator.next().value', iterator.next().value); // Since it was skipped, so it's not assigned
+// const last = iterator.next().value
+// console.log('last', last);