class Node {

    constructor(key) {

        this.Data = key;

        this.Next = null;

    }

}

​

class Queue {

    constructor() {

        this.front = null;

        this.rear = null;

    }

​

    Enqueue(key) {

        let node = new Node(key);

​

        if (this.rear === null) {

            this.front = node;

            this.rear = node;

            return;

        }

​

        this.rear.Next = node;

        this.rear = node;

    }

​

    Dequeue() {

        if (this.front === null) {

            return;