Node.js

Why Node.js?

• ✅ Same language frontend & backend
• ✅ Event-driven, non-blocking I/O
• ✅ Huge npm ecosystem
• ✅ Great for real-time apps
• ✅ Easy to learn for JS developers

Simple HTTP Server

const http = require('http');

const server = http.createServer((req, res) => {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('Hello from Node.js!');
});

server.listen(8000, () => {
    console.log('Server running on :8000');
});

Express.js

const express = require('express');
const app = express();

app.get('/', (req, res) => {
    res.send('Hello from Express!');
});

app.listen(8000, () => {
    console.log('Server running on :8000');
});

PM2 Deployment

# Install PM2
npm install -g pm2

# Start app
pm2 start server.js --name snapcode

# Cluster mode (use all CPUs)
pm2 start server.js -i max --name snapcode

# Save & startup
pm2 save
pm2 startup

ecosystem.config.js

module.exports = {
    apps: [{
        name: 'snapcode',
        script: 'server.js',
        instances: 'max',
        exec_mode: 'cluster',
        env: {
            NODE_ENV: 'production',
            PORT: 8000
        }
    }]
};

Event Loop

// Non-blocking I/O
const fs = require('fs');

// Async (non-blocking)
fs.readFile('file.txt', (err, data) => {
    console.log(data);
});

// This runs immediately, doesn't wait
console.log('Reading file...');

vs Other Runtimes

Aspect	Node.js	Python	Go	PHP
Model	Event loop	Sync/Async	Goroutines	Process pool
Best For	Real-time, APIs	Scripts, ML	Microservices	Web pages
Scaling	PM2 cluster	Gunicorn	Built-in	FPM
Memory	Medium	Medium	Low	Per-request