Linked Lists — A Core Building Block in Data Structures

Arrays usually get all the love. They're easy to use, built into every language, and great for most tasks.

But there’s another data structure that quietly powers a lot of efficient solutions: the linked list.

It’s not about speed for direct access — it’s about flexibility, efficient insertions, and being the foundation for structures like stacks, queues, and even graphs.

Let’s give it the spotlight it deserves.

🤔 What Is a Linked List?

A linked list is a linear data structure made up of nodes.
Each node holds:

• A value
• A reference (or pointer) to the next node

A simple representation:

[10] → [20] → [30] → null

Unlike arrays, elements in a linked list are not stored in contiguous memory. This makes linked lists:

• More memory flexible
• Ideal for fast insertions and deletions
• Slower for direct access to elements by index

🛠️ Use Cases: When Are Linked Lists Useful?

Use a linked list when:

• You need dynamic memory allocation
• You perform frequent insertions/deletions
• You don't require constant-time random access (O(1) index lookup)

Some real-world applications:

• Undo/redo functionality in editors
• Browser history
• Queues and stacks
• Hash table chaining (collision resolution)

🧠 Types of Linked Lists

1. Singly Linked List – Each node points to the next
2. Doubly Linked List – Each node points to both next and previous
3. Circular Linked List – Last node points back to the first node

🧪 Let’s Build a Simple Linked List in JavaScript

Here’s a minimal implementation of a singly linked list:

// Each node in the linked list holds a value and a pointer to the next node
class Node {
  constructor(value) {
    this.value = value; // Store the actual data
    this.next = null;   // Pointer to the next node (default: null)
  }
}

// LinkedList class manages the overall list
class LinkedList {
  constructor() {
    this.head = null; // Start with an empty list
  }

  // Adds a new node at the end of the list
  append(value) {
    const newNode = new Node(value);

    // If list is empty, set head to the new node
    if (!this.head) {
      this.head = newNode;
      return;
    }

    // Otherwise, traverse to the end of the list
    let current = this.head;

    while (current.next) {
      current = current.next;
    }

    // Link the last node to the new node
    current.next = newNode;
  }

  // Prints out the list in a readable format
  print() {
    let current = this.head;
    let output = '';

    // Traverse and build the output string
    while (current) {
      output += `[${current.value}] → `;
      current = current.next;
    }

    output += 'null'; // End of the list
    console.log(output);
  }
}

// Example usage
const list = new LinkedList();
list.append(10);
list.append(20);
list.append(30);
list.print(); // Output: [10] → [20] → [30] → null

⏱️ Time Complexity Overview

⚖️ Pros & Cons

✅ Pros:

• Efficient insertions/deletions
• Dynamic memory use (no resizing)
• Great for stacks, queues, etc.

❌ Cons:

• Slower access time (O(n) for index)
• Uses extra memory (pointers)
• More complex to implement than arrays

🧵 TL;DR

• A Linked List is a dynamic, node-based data structure.
• It’s ideal when you don’t know the final size of your collection.
• Although not as fast for access, it excels in insertions and deletions.
• It lays the foundation for many advanced data structures.

Thanks for reading! 🙌

If you're enjoying the series, feel free to follow me here or check out my YouTube channel for more hands-on dev content.