Anticlockwise spiral conversion of doubly linked list in node js

Js program for Anticlockwise spiral conversion of doubly linked list. Here more information.

// Node JS program for
// Convert a doubly linked list anticlockwise spiral form

// This is Linked List Node
class LinkNode
{
	constructor(data)
	{
		this.data = data;
		this.next = null;
		this.prev = null;
	}
}
class DoublyLinkedList
{
	constructor()
	{
		this.head = null;
		this.tail = null;
	}
	// Insert new node at end position
	insert(value)
	{
		// Create a node
		var node = new LinkNode(value);
		if (this.head == null)
		{
			// Add first node
			this.head = node;
			this.tail = node;
			return;
		}
		// Add node at last position
		this.tail.next = node;
		node.prev = this.tail;
		this.tail = node;
	}
	// Display node element of doubly linked list
	display()
	{
		if (this.head == null)
		{
			console.log("Empty Linked List");
		}
		else
		{
			process.stdout.write("Linked List Head to Tail :");
			// Get first node of linked list
			var temp = this.head;
			// iterate linked list 
			while (temp != null)
			{
				// Display node value
				process.stdout.write("  " + temp.data);
				// Visit to next node
				temp = temp.next;
			}
			process.stdout.write("\nLinked List Tail to Head :");
			// Get last node of linked list
			temp = this.tail;
			// iterate linked list 
			while (temp != null)
			{
				// Display node value
				process.stdout.write("  " + temp.data);
				// Visit to prev node
				temp = temp.prev;
			}
		}
	}
	spiralTransform()
	{
		if (this.head == null || this.head.next == null)
		{
			return;
		}
		var last = this.tail;
		var current = this.head;
		var auxiliary = null;
		var temp = null;
		var back = null;
		// Set new head
		this.head = this.tail;
		while (current != null && last != null)
		{
			if (current == last)
			{
				current.next = null;
				current.prev = back;
				this.tail = current;
				// Set new last node
				return;
			}
			else if (current.next == last)
			{
				current.next = null;
				current.prev = last;
				last.next = current;
				last.prev = back;
				// Set new last node
				this.tail = current;
				return;
			}
			// Swap link
			auxiliary = current.next;
			temp = last.prev;
			current.prev = last;
			last.next = current;
			current.next = temp;
			last.prev = back;
			back = current;
			current = auxiliary;
			last = temp;
		}
	}
}

function main()
{
	var dll = new DoublyLinkedList();
	// Insert following linked list nodes
	dll.insert(1);
	dll.insert(2);
	dll.insert(3);
	dll.insert(4);
	dll.insert(5);
	dll.insert(6);
	dll.insert(7);
	dll.insert(8);
	dll.insert(9);
	console.log("\nBefore anticlockwise spiral conversion");
	// Display all node
	dll.display();
	console.log("\nAfter anticlockwise spiral conversion");
	dll.spiralTransform();
	dll.display();
}
// Start program execution
main();

Output

Before anticlockwise spiral conversion
Linked List Head to Tail :  1  2  3  4  5  6  7  8  9
Linked List Tail to Head :  9  8  7  6  5  4  3  2  1
After anticlockwise spiral conversion
Linked List Head to Tail :  9  1  8  2  7  3  6  4  5
Linked List Tail to Head :  5  4  6  3  7  2  8  1  9