JavaScript Data Structures - 13 - Linked List Overview

Introduction

This tutorial provides an overview of linked lists in JavaScript, a fundamental data structure that allows for efficient data manipulation. Understanding linked lists is crucial for developing algorithms and solving problems in computer science. In this guide, we’ll explore the concept of linked lists, their structure, and how to implement them in JavaScript.

Step 1: Understand the Basics of Linked Lists

• A linked list is a linear data structure composed of nodes.
• Each node contains two elements:
  • Data: The actual value or information.
  • Pointer: A reference to the next node in the sequence.
• The first node is referred to as the head, and the last node points to null.

Practical Tip

• Linked lists are particularly useful for dynamic data storage where the size of the data structure can change frequently.

Step 2: Recognize the Types of Linked Lists

• Singly Linked List: Each node points to the next node. Traversal is one-way.
• Doubly Linked List: Each node points to both the next and previous nodes, allowing two-way traversal.
• Circular Linked List: The last node points back to the head, forming a circular structure.

Common Pitfall

• Forgetting to update pointers can lead to memory leaks or broken links in the list.

Step 3: Implement a Singly Linked List in JavaScript

To create a basic singly linked list, follow these steps:

1. Define the Node Class

   class Node {
       constructor(data) {
           this.data = data;
           this.next = null;
       }
   }
   

2. Define the LinkedList Class

   class LinkedList {
       constructor() {
           this.head = null;
           this.size = 0;
       }
       
       // Method to add a new node
       add(data) {
           const newNode = new Node(data);
           if (!this.head) {
               this.head = newNode;
           } else {
               let current = this.head;
               while (current.next) {
                   current = current.next;
               }
               current.next = newNode;
           }
           this.size++;
       }
   }
   

3. Add Nodes to the List

   const list = new LinkedList();
   list.add(10);
   list.add(20);
   list.add(30);
   

Practical Tip

• Test your linked list implementation by adding, removing, and traversing nodes to ensure correctness.

Step 4: Traverse the Linked List

Implement a method to traverse and display the linked list:

display() {
    let current = this.head;
    while (current) {
        console.log(current.data);
        current = current.next;
    }
}

Step 5: Remove a Node from the Linked List

To remove a node, you need to update the pointers accordingly:

1. Implement the Remove Method

   remove(data) {
       if (!this.head) return;
   
       if (this.head.data === data) {
           this.head = this.head.next;
           this.size--;
           return;
       }
   
       let current = this.head;
       while (current.next) {
           if (current.next.data === data) {
               current.next = current.next.next;
               this.size--;
               return;
           }
           current = current.next;
       }
   }
   

Common Pitfall

• Ensure that you check for the case when the list is empty before attempting to remove a node.

Conclusion

In this tutorial, we explored the concept of linked lists, their types, and how to implement a singly linked list in JavaScript. You learned how to create nodes, add and remove them, and traverse the list. Understanding linked lists will serve as a foundation for more complex data structures and algorithms.

Next Steps

• Experiment with implementing doubly and circular linked lists.
• Explore additional operations like searching and reversing a linked list for deeper understanding.