Queue.js

import LinkedList from '../linked-list/LinkedList';

export default class Queue {
 constructor() {
 this.linkedList = new LinkedList();
 }

 isEmpty() {
 return !this.linkedList.tail;
 }

 peek() {
 if (!this.linkedList.head) {
 return null;
 }

 return this.linkedList.head.value;
 }

 enqueue(value) {
 this.linkedList.append(value);
 }

 dequeue() {
 const removedHead = this.linkedList.deleteHead();
 return removedHead ? removedHead.value : null;
 }

 toString(callback) {
 return this.linkedList.toString(callback);
 }
}