JavaScript Exercises: Count number of nodes in a Singly Linked List

JavaScript Singly Linked List: Exercise-3 with Solution

Count the number of nodes in a SLL

Write a JavaScript program to create a singly linked list of n nodes and count the number of nodes.

Sample Solution:

JavaScript Code:

// Define a class representing a node in a singly linked list
class Node {
    constructor(data) {
        // Initialize the node with provided data
        this.data = data
        // Initialize the next pointer to null
        this.next = null                
    }
}

// Define a class representing a singly linked list
class SinglyLinkedList {
    constructor(Head = null) {
        // Initialize the head of the list
        this.Head = Head
    }

    // Method to add a new node to the end of the list
    add(newNode){
        // Start traversal from the head node
        let node = this.Head;
        // If the list is empty, set the new node as the head and return
        if(node == null){
            this.Head = newNode;
            return;
        }
        // Traverse the list until the last node
        while (node.next) {
            node = node.next;
        }
        // Set the next pointer of the last node to the new node
        node.next = newNode;
    }

    // Method to count the number of nodes in the list
    NodeCount() {
        // Initialize a counter variable
        let ctr = 0;
        // Start traversal from the head node
        let node = this.Head;
        // Traverse the list and increment the counter for each node
        while (node) {
            ctr++;
            node = node.next;
        }
        // Return the total count of nodes
        return ctr;
    } 

    // Method to display the elements of the list
    displayList(){
        // Start traversal from the head node
        let node = this.Head;
        // Initialize an empty string to store the elements of the list
        var str = ""
        // Traverse the list and concatenate each element to the string
        while (node) {
            str += node.data + "->";
            node = node.next;
        }
        // Append "NULL" to indicate the end of the list
        str += "NULL"
        // Print the string containing the list elements
        console.log(str);  
    } 
}

// Create an instance of the SinglyLinkedList class
let numList = new SinglyLinkedList();
// Add nodes with data values to the list
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));
// Display the original elements of the list
console.log("Original Linked list:")
numList.displayList();
// Count the number of nodes in the list
var ctr = numList.NodeCount();
// Display the number of nodes in the list
console.log("Number of elements in the said Linked list: "+ctr)

Output:

Original Linked list:
2->3->4->5->6->7->NULL
Number of elements in the said Linked list: 6

Flowchart:

Live Demo:

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

For more Practice: Solve these Related Problems:

• Write a JavaScript function that traverses a singly linked list iteratively to count its nodes.
• Write a JavaScript function that recursively calculates the length of a singly linked list.
• Write a JavaScript function that converts a singly linked list into an array and returns its length.
• Write a JavaScript function that maintains a counter during node insertions and deletions and verifies the node count by traversing the list.

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