Doubly Linked list implementation using Javascript

DoublyLinkedList.js

/**
 * Javascript implementation of Doubly Linked list
 * 
 * Dinesh
 *
 * (More to come) (Add more error handling scenarios)
 */

// Global object (namespace)
DS = {};

/**
 * DList Nodes
 * 
 */
DS.DListNode = function(){
	this.item = null;
	this.next = null;
	this.prev = null;
}

/**
 * DLinkedList object
 */
DS.DLinkedList = function(){
	this.head = null;
	this.tail = null;
	var size = 0;

	//Insert Nodes
	this.insertNode = function(item){
		var node = new DS.DListNode();
		node.item = item;
		if(this.head == null){
			this.head = node;
			this.tail = node;
			this.tail.next = null;
			this.tail.prev = null;
			size += 1;
		}else{
			var prev = this.tail;
			this.tail.next = node;
			this.tail = node;
			this.tail.prev = prev;
			size += 1;
		}
	}
	
	//Insert node in the first location
	this.insertFirst = function(item){
		var node = new DS.DListNode();
		node.item = item;
		node.next = this.head;
		this.head.prev = node;
		this.head = node;
		size += 1;
	}
	
	// Delete First node
	this.deleteFirstNode = function(){
		if(this.head != null){
			this.head = this.head.next;
			this.head.prev = null;
			size -= 1;
		}else{
			console.log("Linked list is empty");
		}
	}
	
	// Print Nodes
	this.printNodes = function(){
		if(size < 1) console.log("No node present in the Doubly Linked List");
		
		var current = this.head;
		for(var i=0;i<size;i++){
			if(current.prev == null)
				console.log("Node " + current.item + " is at location " + i + " : Previous Node: null : Next Node: "+current.next.item);
			else if(current.next == null)
				console.log("Node " + current.item + " is at location " + i + " : Previous Node: "+current.prev.item + " : Next Node: null");
			else console.log("Node " + current.item + " is at location " + i + " : Previous Node: "+current.prev.item + " : Next Node: "+current.next.item);
			current = current.next;
		}
	}
	
	// Get node Size
	this.getSize = function(){
		return size;
	}
}

var list = new DS.DLinkedList();
list.insertNode("test1");
list.insertNode("test2");
list.insertNode("test3");
list.insertNode("test4");
list.insertNode("test5");
list.insertNode("test6");
list.printNodes();

console.log("Adding item in the start");
list.insertFirst("test1st");
list.printNodes();

console.log("Deleting first node");
list.deleteFirstNode();
list.printNodes();