# JavaScript Exercises: Convert a Doubly Linked lists into a string

## JavaScript Data Structures: Exercise-11 with Solution

Write a JavaScript program to convert a Doubly Linked List into a string and return it.

Sample Solution:

JavaScript Code:

``````class Node {
// Constructor function for creating a new node with a given value
constructor(value) {
this.value = value; // Assign the given value to the node
this.next = null; // Initialize the pointer to the next node as null
this.previous = null; // Initialize the pointer to the previous node as null
}
}

// Constructor function for creating a new doubly linked list with a head node having the given value
constructor(value) {
// Initialize the head node with the given value and no next or previous node
value: value, // Store the value of the head node
next: null, // Pointer to the next node in the list, initially set to null
previous: null // Pointer to the previous node in the list, initially set to null
};
this.length = 0; // Initialize the length of the list to 0
this.tail = this.head; // Set the tail node to the head node initially
}

// Method to add a new node at the end of the list
if (this.head === null) { // Check if the list is empty
this.head = newNode; // If empty, set the new node as the head
this.tail = newNode; // Also set the new node as the tail
} else { // If list is not empty
newNode.previous = this.tail; // Set the previous pointer of the new node to the current tail node
this.tail.next = newNode; // Set the next pointer of the current tail node to the new node
this.tail = newNode; // Update the tail node to the new node
}
this.length++; // Increment the length of the list
}

// Method to convert the doubly linked list into a string
convert_to_string() {
if (!this.head) return ""; // If the list is empty, return an empty string
let current = this.head; // Start from the head of the list
let result = ""; // String to store the values of the nodes
while (current != null) { // Iterate through the list until reaching the end
result += current.value + " "; // Concatenate the value of the current node to the string
current = current.next; // Move to the next node
}
return result; // Return the string containing the values of the nodes
}

// Method to print the values of the nodes in the list
printList() {
let current = this.head; // Start from the head of the list
let result = []; // Array to store the values of the nodes
while (current !== null) { // Iterate through the list until reaching the end
result.push(current.value); // Push the value of the current node to the array
current = current.next; // Move to the next node
}
console.log(result.join(' ')); // Log the values of the nodes separated by space
return this; // Return the DoublyLinkedList object for chaining
}
}

// Create a new instance of the DoublyLinkedList class
let numList = new DoublyLinkedList();
// Add nodes to the list
console.log("Original Doubly Linked Lists:");
numList.printList();
console.log("Converts the said Doubly Linked Lists into a string:");
result = numList.convert_to_string();
console.log(result);

// Create a new instance of the DoublyLinkedList class
let numList1 = new DoublyLinkedList();
console.log("Original Doubly Linked Lists:");
numList1.printList();
console.log("Converts the said Doubly Linked Lists into a string:");
result = numList1.convert_to_string();
console.log(result);
```
```

Output:

```"Original Doubly Linked Lists:"
" 2 3 4 5 6 7"
"Converts the said Doubly Linked Lists into a string:"
"undefined 2 3 4 5 6 7 "
"Original Doubly Linked Lists:"
""
"Converts the said Doubly Linked Lists into a string:"
"undefined "
```

Flowchart:

Live Demo:

See the Pen javascript-doubly-linked-list-exercise-11 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

Linked List Previous: Convert a Doubly Linked lists into an array.
Linked List Next: Get the index of a given element in a Doubly Linked lists.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.

﻿