Sep 1, 2020 · Aug 28, 2020 · Aug 28, 2020 · Aug 29, 2020 · Aug 29, 2020 · Aug 31, 2020
diff --git a/src/data-structures/queues/queue.js b/src/data-structures/queues/queue.js
diff --git a/src/data-structures/queues/queue.spec.js b/src/data-structures/queues/queue.spec.js
Original file line number	Diff line number	Diff line change
		@@ -1,18 +1,31 @@
		const LinkedList = require('../linked-lists/linked-list');

	/* Usage Example:
	// tag::snippet[]
	const queue = new Queue();

	queue.enqueue('a');
	queue.enqueue('b');
	queue.dequeue(); //↪️ a
	queue.enqueue('c');
	queue.dequeue(); //↪️ b
	queue.dequeue(); //↪️ c
	// end::snippet[]
	// */

		// tag::constructor[]
		/**
		* Data structure where we add and remove elements in a first-in, first-out (FIFO) fashion
		*/
		class Queue {
	constructor() {
	this.items = new LinkedList();
	constructor(iterable = []) {
	this.items = new LinkedList(iterable);
		}
		// end::constructor[]

		// tag::enqueue[]
		/**
	* Add element to the queue
	* Add element to the back of the queue.
		* Runtime: O(1)
		* @param {any} item
		* @returns {queue} instance to allow chaining.
Expand All		@@ -25,7 +38,7 @@ class Queue {

		// tag::dequeue[]
		/**
	* Remove element from the queue
	* Remove element from the front of the queue.
		* Runtime: O(1)
		* @returns {any} removed value.
		*/
Expand All		@@ -47,23 +60,30 @@ class Queue {
		isEmpty() {
		return !this.items.size;
		}

	/**
	* Return the most recent value or null if empty.
	*/
	back() {
	if (this.isEmpty()) return null;
	return this.items.last.value;
	}

	/**
	* Return oldest value from the queue or null if empty.
	* (Peek at the next value to be dequeue)
	*/
	front() {
	if (this.isEmpty()) return null;
	return this.items.first.value;
	}
		}

		// Aliases
	Queue.prototype.peek = Queue.prototype.front;
		Queue.prototype.add = Queue.prototype.enqueue;
	Queue.prototype.push = Queue.prototype.enqueue;
		Queue.prototype.remove = Queue.prototype.dequeue;
	Queue.prototype.pop = Queue.prototype.dequeue;

		module.exports = Queue;

	/* Usage Example:
	// tag::snippet[]
	const queue = new Queue();

	queue.enqueue('a');
	queue.enqueue('b');
	queue.dequeue(); //↪️ a
	queue.enqueue('c');
	queue.dequeue(); //↪️ b
	queue.dequeue(); //↪️ c
	// end::snippet[]
	// */
Original file line number	Diff line number	Diff line change
Expand Up		@@ -46,4 +46,28 @@ describe('Queue', () => {
		expect(queue.isEmpty()).toBe(false);
		});
		});

	describe('#back', () => {
	it('should return null if empty', () => {
	expect(queue.back()).toEqual(null);
	});

	it('should return newest element', () => {
	queue.enqueue('oldest');
	queue.enqueue('newest');
	expect(queue.back()).toEqual('newest');
	});
	});

	describe('#front', () => {
	it('should return null if empty', () => {
	expect(queue.front()).toEqual(null);
	});

	it('should return oldest element', () => {
	queue.enqueue('oldest');
	queue.enqueue('newest');
	expect(queue.front()).toEqual('oldest');
	});
	});
		});