JavaScript Exercises: Get index of an given element in a Singly Linked list

JavaScript Singly Linked List: Exercise-17 with Solution

Write a JavaScript program to get the index of an element in a Singly Linked list.

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 find the index of a given element in the list
    index_of(el) {
        let index = 0;
        let node = this.Head; 
        // Traverse the list until the end or until the element is found
        while (node) {
            // If the data of the current node matches the element, return the index
            if (node.data === el) {
                return index;
            }
            // Move to the next node and increment the index
            node = node.next;
            index++;
        }
        // If the element is not found, return -1
        return -1;
    }

    // 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(12));
numList.add(new Node(13));
numList.add(new Node(14));
numList.add(new Node(15));
numList.add(new Node(14));
numList.add(new Node(16));
// Display the elements of the list
console.log("Singly Linked list:")
numList.displayList();
// Find the index of various elements in the list
result = numList.index_of(12);
console.log("Index of 12 in the said linked list: " + result);
result = numList.index_of(13);
console.log("Index of 13 in the said linked list: " + result);
result = numList.index_of(14);
console.log("Index of 14 in the said linked list: " + result);
result = numList.index_of(16);
console.log("Index of 16 in the said linked list: " + result);

Output:

Singly Linked list:
12->13->14->15->14->16->NULL
Index of 12 in the said link list: 0
Index of 13 in the said link list: 1
Index of 14 in the said link list: 2
Index of 16 in the said link list: 5

Flowchart:

Live Demo:

See the Pen javascript-singly-linked-list-exercise-17 by w3resource (@w3resource) on CodePen.

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