Stack.js

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

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

 /**
 * @return {boolean}
 */
 isEmpty() {
 return !this.linkedList.tail;
 }

 /**
 * @return {*}
 */
 peek() {
 if (this.isEmpty()) {
 return null;
 }

 return this.linkedList.tail.value;
 }

 /**
 * @param {*} value
 */
 push(value) {
 this.linkedList.append(value);
 }

 /**
 * @return {*}
 */
 pop() {
 const removedTail = this.linkedList.deleteTail();
 return removedTail ? removedTail.value : null;
 }

 /**
 * @return {*[]}
 */
 toArray() {
 return this.linkedList
 .toArray()
 .map(linkedListNode => linkedListNode.value)
 .reverse();
 }

 /**
 * @param {function} [callback]
 * @return {string}
 */
 toString(callback) {
 return this.linkedList.toString(callback);
 }
}