Linked Lists

Linked List Implementation

// declare the LinkedList constructor function
function LinkedList() {
  this.head = null;
  this.tail = null;
}

// declare the Node constructor function
function Node(value, next, prev) {
  this.value = value;
  this.next = next;
  this.prev = prev;
}

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.removeHead = function() {
  if (!this.head) {
    return null;
  }

  var val = this.head.value;
  this.head = this.head.next;

  if (this.head) {
    this.head.prev = null;
  } else {
    this.tail = null;
  }

  return val;
}

LinkedList.prototype.removeTail = function() {
  if (!this.tail) {
    return null;
  }

  var val = this.tail.value;
  this.tail = this.tail.prev;

  if (this.tail) {
    this.tail.next = null;
  } else {
    this.head = null;
  }

  return val;
}

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

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