Doubly linked lists

There are different types of linked lists. In this section, we are going to cover the doubly linked list. The difference between a doubly linked list and a normal linked list is that in a linked list, we make the link from one node to the next one only, while in the doubly linked list, we have a double link: one for the next element and one for the previous element, as shown in the following diagram:

Let's get started with the changes that are needed to implement the DoublyLinkedList class:

function DoublyLinkedList() { 
 
 let Node = function(element){ 
 
   this.element = element; 
   this.next = null; 
   this.prev = null; //NEW 
 }; 
 
 let length = 0; 
 let head = null; 
 let tail = null; //NEW 
 
 //methods here 
} 

As we can see in this code, the differences between the LinkedList class and the DoublyLinkedList class are marked by NEW. Inside the Node class, we have the prev attribute (a...