// LinkedList and Node function Constructor

function LinkedList() {

this.head = null;

this.tail = null;

};

function Node(value, next, prev) {

this.value = value;

this.next = next;

this.prev = prev;

};

// Add to head

LinkedList.prototype.addHead = function(value) {

var newNode = new Node(value, this.head, null);

if(this.head) {

this.head.prev = newNode;

} else {

this.tail = newNode;

}

this.head = newNode;

};

var LL = new LinkedList();

LL.addHead(100);

LL.addHead(200);

LL.addHead(300);

LL.addHead(200);

console.log(LL);

// Add to tail

LinkedList.prototype.addTail = function(value) {

var newNode = new Node(value, null, this.tail);

if(this.tail) {

this.tail.next = newNode;

}else {

this.head = newNode;

}

this.tail = newNode;

};

LL.addTail(100);

LL.addTail(200);

LL.addTail(300);

console.log(LL);

console.log(ll.head.value);

// Remove from head

LinkedList.prototype.removeHead = function(){

if(this.head == null) {

return null;

}

else {

var val = this.head.value;

this.head = this.head.next;

}

if(!this.head) this.tail = null;

return val;

};

var ll = new LinkedList();

console.log(LL.removeHead());

console.log(LL);

// Remove from tail

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;

}

console.log(LL.removeTail());

console.log(LL.removeTail());

console.log(LL.removeTail());

console.log(LL);

// search in LinkedList

LinkedList.prototype.search = function(searchValue) {

if(!this.head) return null;

var currentNode = this.head;

while(currentNode){

if(currentNode.value === searchValue) return currentNode.value;

currentNode = currentNode.next;

}

return null;

}

console.log(LL.search(100));

// find indexOf element in LinkedList

LinkedList.prototype.indexOf = function(value) {

if(!this.head) return null;

var currentNode = this.head;

var counter = 0;

var indexArr = new Array;

while(currentNode){

if(currentNode.value === value){

indexArr.push(counter);

}

counter++;

currentNode = currentNode.next;

}

return indexArr;

}

console.log(LL.indexOf(200));