Doubly Linked List in JavaScript

Doubly linked lists are those lists where each node has references to both the next and previous node.
A doubly linked list consists of three elements:

Value.
Previous pointer.
Next pointer to the previous or next node, respectively, or null.

The first node is called head and the last node is called tail.

In the following example we will show a Doubly linked list with its methods to add, remove, show, etc.

<script>
  class Node {
    constructor(value) {
      this.value = value;  
      this.previous = null; 
      this.next = null;
    }
  }
  class DoublyLinkedList {
    constructor(value) {
      this.head = {
        value: value,
        next: null,
        previous: null
      };
      this.length = 1;
      this.tail = this.head;
    }
	//Print List
    print() {
      let array = [];
      let myList = this.head;
      while (myList !== null) {
        array.push(myList.value);
        myList = myList.next;
      }

      console.log(array.join(' | '));
      return this;
    }

    //insert node at end of list
    appendNode(value) {
      let myNode = new Node(value);

      this.tail.next = myNode;
      myNode.previous = this.tail;
      this.tail = myNode;

      this.length++;
    }

    //Insert node at the start of the Doubly list
    prependNode(value) {
      let myNode = new Node(value);

      myNode.next = this.head;
      this.head.previous = myNode;
      this.head = myNode;

      this.length++;
    }

    // Insert node at a index of the list
    insertNode(index, value){
      if (!Number.isInteger(index) || index < 0 || index > this.length + 1) {
        console.log('Invalid index. Current length is '+$(this.length));
        return this;
      }
      if (index === 0) {
        this.prepend(value);
        return this;
      }
      if (index === this.length) {
        this.append(value);
        return this;
      }
      let myNode = new Node(value);
      let previousNode = this.head;

      for (let k = 0; k < index - 1; k++) {
        previousNode = previousNode.next;
      }

      let nextNode = previousNode.next;

      myNode.next = nextNode;
      previousNode.next = myNode;
      myNode.previous = previousNode;
      nextNode.previous = myNode;

      this.length++;
    }

    //Remove Node according to index
    removeNode(index) {
      if (!Number.isInteger(index) || index < 0 || index > this.length) {
        console.log(`Invalid index. Current length is ${this.length}.`);
        return this;
      }
      if (index === 0) {
        this.head = this.head.next;
        this.head.previous = null;

        this.length--;
        return this;
      }
      // Remove tail
      if (index === this.length - 1) {
        this.tail = this.tail.previous;
        this.tail.next = null;

        this.length--;
        return this;
      }

      // Remove node at an index
      let previousNode = this.head;

      for (let k = 0; k < index - 1; k++) {
        previousNode = previousNode.next;
      }
      let deleteNode = previousNode.next;
      let nextNode = deleteNode.next;

      previousNode.next = nextNode;
      nextNode.previous = previousNode;

      this.length--;
      return this;
    }
  }

  let exampleDoublyList = new DoublyLinkedList(5);
  console.log('I create the Doubly List with the value 5');
  exampleDoublyList.print();
  console.log('I add at the end of the list the value 6');
  exampleDoublyList.appendNode(6);
  exampleDoublyList.print();
  console.log('I add at the end of the list the value 8');
  exampleDoublyList.appendNode(8);
  console.log('I add at the end of the list the value 12');
  exampleDoublyList.appendNode(12);
  exampleDoublyList.print();
  exampleDoublyList.prependNode(4);
  console.log('I add at the beginning of the list the value 4');
  exampleDoublyList.print();
  console.log('Insert at index 1 the value 3');
  exampleDoublyList.insertNode(1, 3);
  exampleDoublyList.print();  
  console.log('Insert at index 4 the value 20');
  exampleDoublyList.insertNode(4, 20);
  exampleDoublyList.print();
  console.log('I remove the value 1 and the value 3');
  exampleDoublyList.removeNode(1);
  exampleDoublyList.removeNode(3);
  exampleDoublyList.print();
</script>