JavaScript program for searching for elements in a linked list

A linked list is a linear data structure in which each element (also called a node) contains a data value and a reference to the next node in the list. A common operation on a linked list is to search for a specific element. This involves walking through the list and comparing each node's data value to the target element until a match is found.

This is an example of a linked list we will use throughout this article -

10 -> 20 -> 30 -> 40 -> Empty

In this linked list, each node contains a value, and the arrow indicates the next node in the sequence. The list starts with the head node, which contains the value 10, and ends with the tail node, which contains the value 40 and points to null. We will use this linked list to demonstrate how to search for an element in a linked list using JavaScript.

Let’s look at the following example -

Linked list: 10 -> 20 -> 30 -> 40 -> null
Input: 40
Output: Element found at index 3
Input: 10
Output: Element found at index 0
Input: null
Output: Element not found

Now let’s discuss the algorithm for creating linked lists in JavaScript.

algorithm

Step 1 - Define a Node class with two properties: value and next. The value attribute represents the data stored in the node, and the next attribute is a reference to the next node in the linked list.

Step 2 - Define a LinkedList class with three properties: head, tail and length. The head attribute represents the first node in the linked list, the tail attribute represents the last node in the linked list, and the length attribute represents the number of nodes in the linked list.

Step 3 - Define a method named - add to the LinkedList class that takes a value as a parameter. The add method should create a new node with the given value and add it to the end of the linked list.

Step 4 - Define a method called "remove" for the LinkedList class that takes a value as a parameter. The remove method should remove the first node with a given value in the linked list.

Step 5 - Define a method called search for the LinkedList class that takes a value as a parameter. The search method should return the first node in the linked list with the given value, or null if the node is not found.

Step 6 - Define a method named reverse for the LinkedList class, which is used to reverse the order of nodes in the linked list.

Example: Using JavaScript to implement the above algorithm

The following program defines a Node class and a LinkedList class. The Node class creates a new node using the given data value and a reference to the next node in the list. The LinkedList class creates a new linked list with the head node initially pointing to null and the size property set to 0. The add method adds a new node to the end of the linked list. The search method traverses the linked list and returns the index of the element if found, or a message if not found. Finally, the program creates a new linked list, adds elements to it, and searches for a specific element.

// Define the Node class for a singly linked list
class Node {
   constructor(data) {
      this.data = data;
      this.next = null;
   }
}
// Define the LinkedList class
class LinkedList {
   constructor() {
      this.head = null;
      this.size = 0;
   }
   // Add an element to the linked list
   add(element) {
      const node = new Node(element);
      // If the linked list is empty, set the new node as the head
      if (this.head === null) {
         this.head = node;
      } else {
         // Traverse to the end of the linked list and add the new node
         let current = this.head;
         while (current.next !== null) {
            current = current.next;
         }
         current.next = node;
      }
      this.size++;
   }
   // Search for an element in the linked list
   search(element) {
      let current = this.head;
      let index = 0;
      // Traverse through the linked list until the element is found
      while (current !== null) {
         if (current.data === element) {
            return `Element found at index ${index}`;
         }
         current = current.next;
         index++;
      }
      return "Element not found";
   }
}
// Create a new linked list
const ll = new LinkedList();
// Add elements to the linked list
ll.add(10);
ll.add(20);
ll.add(30);
ll.add(40);
ll.add(50);
// Search for an element in the linked list
const result = ll.search(30);
console.log(result); 

in conclusion

The procedure for searching for elements in a linked list using JavaScript involves creating a "LinkedList" class that defines methods for adding elements to the list and for searching for elements in the list. The program uses a while loop to traverse the linked list and compare the data element in each node to the element it is looking for. If the element is found, the program returns the index of the node, if the element is not found, the program returns "Element not find".

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