JavaScript Exercises: Get the value of a node at a given position in a Doubly Linked List

JavaScript Data Structures: Exercise-8 with Solution

Write a JavaScript program to get the value of a node at a given position in a Doubly Linked List.

Sample Solution:

JavaScript Code:

 class Node {
         constructor(value) {
                  this.value = value;
                  this.next = null;
                  this.previous = null;
         }
}
class DoublyLinkedList {
         constructor(value) {
                  this.head = {
                            value: value,
                            next: null,
                            previous: null
                  };
                  this.length = 0;
                  this.tail = this.head;
         }
         // Insert node at end of the list
 add(newNode) {
   if (this.head === null) {
   this.head = newNode;
   this.tail = newNode;
   }
   else
   {
   newNode.previous = this.tail;
   this.tail.next = newNode;
   this.tail = newNode;
 }
 this.length++;
  }
 insertAt(position, data) {
 if (position < 0 || position > this.length) {
   return false;
 }
 var newNode = {
   value: data,
   next: null,
   previous: null
 };
 if (this.length === 0) {
   this.head = newNode;
   this.tail = newNode;
 } else if (position === 0) {
   newNode.next = this.head;
   this.head.previous = newNode;
   this.head = newNode;
 } else if (position === this.length) {
   this.tail.next = newNode;
   newNode.previous = this.tail;
   this.tail = newNode;
 } else {
   var current = this.head;
   var index = 0;
   while (index < position) {
     current = current.next;
     index++;
   }
   newNode.next = current;
   newNode.previous = current.previous;
   current.previous.next = newNode;
   current.previous = newNode;
 }
 this.length++;
 return true;
 }
get_Node_Value(index) {
 if (index < 0 || index >= this.length) {
   return null;
 }
 var current = this.head;
 var count = 0;
 while (count < index) {
   current = current.next;
   count++;
 }
 return current.value;
}
 printList() {
                  let current = this.head;
                  let result = [];
                  while (current !== null) {
                            result.push(current.value);
                            current = current.next;
                  }
                  console.log(result.join(' '));
                  return this;
         }
}
let numList = new DoublyLinkedList();
numList.add(new Node(2));
numList.add(new Node(3));
numList.add(new Node(4));
numList.add(new Node(5));
numList.add(new Node(6));
numList.add(new Node(7));
console.log("Original Doubly Linked Lists:")
numList.printList();
console.log("Value at index 1:")
console.log(numList.get_Node_Value(1));
console.log("Value at index 5:")
console.log(numList.get_Node_Value(5));
console.log("Value at index 11:")
console.log(numList.get_Node_Value(11));

Sample Output:

"Original Doubly Linked Lists:"
" 2 3 4 5 6 7"
"Value at index 1:"
2
"Value at index 5:"
6
"Value at index 11:"
null 

Flowchart:

Live Demo:

See the Pen javascript-doubly-linked-list-exercise-8 by w3resource (@w3resource) on CodePen.

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