JavaScript Data Structures: Doubly Linked List: Get a specific node by its index

class Node { constructor(value) { this.value = value; this.prev = null; this.next = null; } } class DoublyLinkedList { constructor() { this.length = 0; this.head = null; this.tail = null; } push(value) { const newNode = new Node(value); if (!this.length) { this.head = newNode; this.tail = newNode; } else { this.tail.next = newNode; newNode.prev = this.tail; this.tail = newNode; } this.length += 1; return newNode; } } 

// current list: A (head) <===> B <===> C (tail) // desired node: get(0); // A (starting from head) get(1); // B (starting node doesn't matter, equal distance from head or tail) get(2); // C (starting from tail) 

class Node { constructor(value) { this.value = value; this.prev = null; this.next = null; } } class DoublyLinkedList { constructor() { this.length = 0; this.head = null; this.tail = null; } push(value) { const newNode = new Node(value); if (!this.length) { this.head = newNode; this.tail = newNode; } else { this.tail.next = newNode; newNode.prev = this.tail; this.tail = newNode; } this.length += 1; return newNode; } get(index) { // if list is empty, if index is less than 0, or if index is greater than or equal to the list length, return null if (!this.length || index < 0 || index >= this.length) { return null; } else { let currentNode; // if the desired node is in the bottom half of the list if (index < this.length / 2) { // add counter, starting from 0 and counting upwards in the loop let counter = 0; // start from the head currentNode = this.head; // go to the next node until we found our desired node while (counter < index) { currentNode = currentNode.next; counter += 1; } } else { // add counter, starting from the top and counting downwards in the loop let counter = this.length - 1; // start from the tail currentNode = this.tail; // go to the previous node until we found our desired node while (counter > index) { currentNode = currentNode.prev; counter -= 1; } } // return node return currentNode; } } } 

const newDLL = new DoublyLinkedList(); newDLL.push("A"); newDLL.push("B"); newDLL.push("C"); // nothing to see console.log(newDLL.get(-1)); // null // should be A console.log(newDLL.get(0)); // <ref *1> Node { // value: 'A', // prev: null, // next: <ref *2> Node { // value: 'B', // prev: [Circular *1], // next: Node { value: 'C', prev: [Circular *2], next: null } // } // } // should be B console.log(newDLL.get(1)); // <ref *1> Node { // value: 'B', // prev: Node { value: 'A', prev: null, next: [Circular *1] }, // next: Node { value: 'C', prev: [Circular *1], next: null } // } // should be C console.log(newDLL.get(2)); // <ref *2> Node { // value: 'C', // prev: <ref *1> Node { // value: 'B', // prev: Node { value: 'A', prev: null, next: [Circular *1] }, // next: [Circular *2] // }, // next: null // } // nothing to see console.log(newDLL.get(3)); // null