queues.js

class Node {
    constructor(val) {
        this.val = val;
        this.next = null;
    }
}

module.exports = class Queue {
    constructor () {
        this.first = null;
        this.last = null;
        this.size = 0;
    }
    enqueue(val) {
        const newNode = new Node(val);
        if(!this.first) {
            this.head = newNode;
            this.last = newNode;
        } else {
            this.last.next = newNode;
            this.last = newNode;
        }
        this.size++;
        return newNode;
    }
    dequeue() {
        if(!this.first) return null;
        var temp = this.first;
        if(this.first === this.last) {
            this.last = null;
        }
        this.first = this.first.next;
        this.size--;
        return temp.val;
    }
    print() {
        var arr = [];
        var current = this.head;
        while(current) {
            arr.push(current.val);
            current = current.next;
        }
        console.log(arr);
    }
}