Chapter 2Node.js & Express~1 min read

Modules आणि npm

Code Organize करा, Packages वापरा

Node.js मध्ये code modules मध्ये organize केला जातो. Built-in modules (fs, path, http) already available असतात. npm ने third-party packages install करता येतात.

CommonJS modules (require/module.exports)

javascript

// math.js — module define करा
function add(a, b) { return a + b; }
function subtract(a, b) { return a - b; }

module.exports = { add, subtract };

// app.js — module import करा
const { add, subtract } = require('./math');
console.log(add(5, 3));      // 8
console.log(subtract(10, 4)); // 6

ES Modules (import/export) — modern way

javascript

// package.json मध्ये "type": "module" लावा
// math.mjs किंवा .js with "type": "module"

export function add(a, b) { return a + b; }
export const PI = 3.14159;

// app.js
import { add, PI } from './math.js';
console.log(add(2, 3)); // 5

npm — Package Manager

bash

# Project initialize करा
npm init -y

# Package install करा
npm install express         # runtime dependency
npm install nodemon --save-dev  # dev dependency

# Package.json scripts
# "scripts": { "start": "node app.js", "dev": "nodemon app.js" }

# Script run करा
npm run dev

# Packages बघा
npm list

# Update
npm update express

# Uninstall
npm uninstall lodash

Built-in Modules

▸fs — File System (files read/write)
▸path — File paths manipulate
▸http/https — HTTP server बनवा
▸os — Operating system info
▸events — EventEmitter
▸crypto — Hashing, encryption

✅ Key Points — लक्षात ठेवा

▸require() / import — module import करा
▸module.exports / export — module export करा
▸npm install — packages add करा
▸package.json — project manifest
▸node_modules — installed packages (git ignore करा)

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Express.js — पहिला Server