merge: Refactor Code and Add test case (TheAlgorithms#845)

Author: Yatin-kathuria

Data-Structures/Queue/Queue.js

@@ -5,49 +5,52 @@
 * implementation uses an array to store the queue.
 */
 
-// Functions: enqueue, dequeue, peek, view, length
-
-const Queue = (function () {
+// Functions: enqueue, dequeue, peek, view, length, empty
+class Queue {
  // constructor
- function Queue () {
+ constructor () {
  // This is the array representation of the queue
  this.queue = []
  }
 
  // methods
  // Add a value to the end of the queue
- Queue.prototype.enqueue = function (item) {
+ enqueue (item) {
  this.queue.push(item)
  }
 
  // Removes the value at the front of the queue
- Queue.prototype.dequeue = function () {
- if (this.queue.length === 0) {
+ dequeue () {
+ if (this.empty()) {
  throw new Error('Queue is Empty')
  }
 
- const result = this.queue[0]
- this.queue.splice(0, 1) // remove the item at position 0 from the array
-
- return result
+ return this.queue.shift() // remove the item at position 0 from the array and return it
  }
 
  // Return the length of the queue
- Queue.prototype.length = function () {
+ length () {
  return this.queue.length
  }
 
  // Return the item at the front of the queue
- Queue.prototype.peek = function () {
+ peek () {
+ if (this.empty()) {
+ throw new Error('Queue is Empty')
+ }
+
  return this.queue[0]
  }
 
  // List all the items in the queue
- Queue.prototype.view = function (output = value => console.log(value)) {
+ view (output = value => console.log(value)) {
  output(this.queue)
  }
 
- return Queue
-}())
+ // Return Is queue empty ?
+ empty () {
+ return this.queue.length === 0
+ }
+}
 
 export { Queue }

Data-Structures/Queue/test/Queue.test.js

@@ -0,0 +1,48 @@
+import { Queue } from '../Queue'
+
+describe('Queue', () => {
+ it('Check enqueue/dequeue', () => {
+ const queue = new Queue()
+ queue.enqueue(1)
+ queue.enqueue(2)
+ queue.enqueue(8)
+ queue.enqueue(9)
+
+ expect(queue.dequeue()).toBe(1)
+ expect(queue.dequeue()).toBe(2)
+ })
+
+ it('Check length', () => {
+ const queue = new Queue()
+
+ queue.enqueue(1)
+ queue.enqueue(2)
+ queue.enqueue(8)
+ queue.enqueue(9)
+
+ expect(queue.length()).toBe(4)
+ })
+
+ it('Check peek', () => {
+ const queue = new Queue()
+
+ queue.enqueue(1)
+ queue.enqueue(2)
+ queue.enqueue(8)
+ queue.enqueue(9)
+
+ expect(queue.peek()).toBe(1)
+ })
+
+ it('Check empty', () => {
+ const queue = new Queue()
+ expect(queue.empty()).toBeTruthy()
+
+ queue.enqueue(1)
+ queue.enqueue(2)
+ queue.enqueue(8)
+ queue.enqueue(9)
+
+ expect(queue.empty()).toBeFalsy()
+ })
+})