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

JavaScript Data Structures: Exercise-3 with Solution

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

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++;
}
  
  size() {
		return this.length;
	}

  is_Empty(){
      return this.length === 0;
    };

 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(5));
numList.add(new Node(6));
numList.add(new Node(8));
console.log("Original Doubly Linked Lists:")
numList.printList();
let linkedlist_empty = numList.is_Empty();
console.log("Check the said Doubly Linked lists is empty or not! "+linkedlist_empty);
new_numList = new DoublyLinkedList();
new_numList.printList();
linkedlist_empty = new_numList.is_Empty();
console.log("Check 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:

Flowchart: JavaScript  Exercises: Count number of nodes in a Doubly Linked Lists.

Live Demo:

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


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Linked List Previous: Count number of nodes in a Doubly Linked Lists.
Linked List Next: Head and Tail of a Doubly Linked Lists.

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JavaScript: Tips of the Day

Shorten an array using its length property

A great way of shortening an array is by redefining its length property.

let array = [0, 1, 2, 3, 4, 5, 6, 6, 8, 9]
array.length = 4
// Result: [0, 1, 2, 3]

Important to know though is that this is a destructive way of changing the array. This means you lose all the other values that used to be in the array.

Ref: https://bit.ly/2LBj213