JavaScript Exercises: Check whether a Doubly Linked Lists is empty or not

JavaScript Data Structures: Exercise-3 with Solution

Check if a DLL is empty

Write a JavaScript program to check whether a Doubly Linked Lists is empty or not. Return true otherwise false.

Sample Solution:

JavaScript Code:

// Define a class for a Node in a doubly linked list
class Node {
	constructor(value) {
		this.value = value;
		this.next = null;
		this.previous = null;
	}
}
// Define a class for a Doubly Linked List
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++;
	}
	// Get the size of the linked list
	size() {
		return this.length;
	}
	// Check if the linked list is empty
	is_Empty() {
		return this.length === 0;
	};
	// Print the linked list
	printList() {
		let current = this.head;
		let result = [];
		while (current !== null) {
			result.push(current.value);
			current = current.next;
		}
		console.log(result.join(' '));
		return this;
	}
}
// Create a new doubly linked list
let numList = new DoublyLinkedList();
// Add nodes to the linked list
numList.add(new Node(2));
numList.add(new Node(3));
numList.add(new Node(5));
numList.add(new Node(6));
numList.add(new Node(8));
// Display the original doubly linked list
console.log("Original Doubly Linked Lists:");
numList.printList();
// Check if the linked list is empty
let linkedlist_empty = numList.is_Empty();
console.log("Check if the said Doubly Linked lists is empty or not! " + linkedlist_empty);
// Create a new empty doubly linked list
let new_numList = new DoublyLinkedList();
// Display the new empty doubly linked list
new_numList.printList();
// Check if the new doubly linked list is empty
linkedlist_empty = new_numList.is_Empty();
console.log("Check if the said Doubly Linked lists is empty or not! " + linkedlist_empty);

Sample Output:

Original Doubly Linked Lists:
 2 3 5 6 8
Check the said Doubly Linked lists is empty or not! false

Check the said Doubly Linked lists is empty or not! true

Flowchart:

Live Demo:

See the Pen javascript-doubly-linked-list-exercise-3 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that checks if the head pointer of a doubly linked list is null to determine emptiness.
• Write a JavaScript function that returns a boolean indicating whether a doubly linked list is empty by checking both head and tail.
• Write a JavaScript function that validates a DLL and returns a custom message if the list has no nodes.
• Write a JavaScript function that uses conditional statements to confirm if a doubly linked list is empty.

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