1. Definition

Modules in Node.js are reusable blocks of code that can be imported and used in different files. They help organize code into smaller, manageable parts.

2. Types of Modules

• Core Modules: Built into Node.js (e.g., http, fs)
• Local Modules: Custom modules created by developers
• Third-party Modules: Installed using npm (e.g., express)

3. Why We Use Modules

• Organize code into smaller parts
• Improve code reusability
• Make applications easier to maintain
• Avoid code duplication

4. How Modules Work

• Export functionality using module.exports
• Import using require()
• Each file acts as a separate module

5. Example

👉 math.js (module file)

function add(a, b) {
  return a + b;
}

module.exports = add;

👉 app.js (main file)

const add = require("./math");

console.log(add(2, 3));

6. Advantages

• Better code organization
• Reusable components
• Easy maintenance
• Scalable applications

7. Disadvantages

• Too many modules can increase complexity
• Requires proper structure and management