Day 2: Modules and NPM - Node.js Tutorial

Modules are reusable pieces of code that can be shared across different parts of your application. Node.js has a built-in module system that allows you to organize your code into separate files.

Built-in Modules:
Node.js comes with many built-in modules that provide core functionality:
• fs - File system operations
• http - HTTP server and client
• path - File path utilities
• os - Operating system utilities
• crypto - Cryptographic functionality
• url - URL parsing and formatting

Creating Custom Modules:
You can create your own modules using module.exports to export functions, objects, or values. Other files can then import these modules using require().

NPM (Node Package Manager):
NPM is the default package manager for Node.js. It helps you install, manage, and share packages. The package.json file contains metadata about your project and its dependencies.

Installing Packages:
Use npm install to install packages locally or globally. Local packages are installed in node_modules folder and are specific to your project.

Package.json:
This file contains project metadata including name, version, dependencies, scripts, and more. It's essential for managing your Node.js project.

Interactive Examples

Creating a Custom Module

Creating and using a custom math module

JavaScript

// math.js - Custom module
const add = (a, b) => a + b;
const subtract = (a, b) => a - b;
const multiply = (a, b) => a * b;
const divide = (a, b) => a / b;

module.exports = {
  add,
  subtract,
  multiply,
  divide
};

// app.js - Using the custom module
const math = require('./math');

console.log('Addition:', math.add(5, 3));
console.log('Subtraction:', math.subtract(10, 4));
console.log('Multiplication:', math.multiply(6, 7));
console.log('Division:', math.divide(20, 4));

Output

Addition: 8
Subtraction: 6
Multiplication: 42
Division: 5

Explanation

This example shows how to create a custom module with math functions and import it in another file using require().