Linked list in JavaScript

linked-list.js

/**
 * Read the original blog post for a detailed explanation!
 * http://www.nickang.com/linked-list-explained-part-1/
 * http://www.nickang.com/linked-list-implementation-part-2/
 */

/**
 * Constructor functions
 */

function LinkedList() {
  this.head = null;
  this.tail = null;
}

function Node(value, next, prev) {
  this.value = value;
  this.next = next;
  this.prev = prev;
}

/**
 * Methods added to prototype chain
 */

LinkedList.prototype.addToHead = function(value) {
  var newNode = new Node(value, this.head, null);
  
  if (this.head) this.head.prev = newNode;
  else this.tail = newNode;

  this.head = newNode;
};

LinkedList.prototype.addToTail = function(value) {
  var newNode = new Node(value, null, this.tail);
  
  if (this.tail) this.tail.next = newNode;
  else this.head = newNode;
  
  this.tail = newNode;
};

LinkedList.prototype.removeFromHead = function() {
  // empty list, return null
  if (!this.head) return null;

  var value = this.head.value;
  
  // update head pointer to new head
  this.head = this.head.next;
  
  if (this.head) this.head.prev = null;
  else this.tail = null; // linked list is empty

  return value;
};

LinkedList.prototype.removeFromTail = function() {
  if (!this.tail) return null;
  
  var value = this.tail.value;
  
  this.tail = this.tail.prev;
  
  if (this.tail) this.tail.next = null;
  else this.head = null;
  
  return value;
}

LinkedList.prototype.search = function(searchValue) {
  var currentNode = this.head;
  
  while (currentNode) {
    if (currentNode.value === searchValue) return currentNode;
    currentNode = currentNode.next;
  }
  return null;
}

LinkedList.prototype.indexOf = function(searchValue) {
  var currentNode = this.head;
  var currentIndex = 0;
  var indexes = [];
  
  while (currentNode) {
    if (currentNode.value === searchValue) indexes.push(currentIndex);
    currentNode = currentNode.next;
    currentIndex++;
  }
  return indexes;
}


var ll = new LinkedList();

ll.addToHead(10);
ll.addToTail(15);
ll.addToTail(99);
ll.addToTail(105);
ll.addToTail(40);
ll.addToTail(20);
ll.removeFromTail();

console.log('LOG: linked list object');
console.log(ll);  // should show head as node with 10 and tail as node with 40
console.log('\nLOG: search for node with 99');
console.log(ll.search(99));  // should show node object with value 99
console.log('\nLOG: find indexOf node with 99');
console.log(ll.indexOf(99));  // should log [2]