Node.js Event Loop — The Sync Crypto Gotcha

/* 
 * Package: io.thecodeforge.node.basics
 */
const fs = require('fs');

console.log('1. Initiating non-blocking file read...');

// fs.readFile is asynchronous and non-blocking
fs.readFile('large-report.pdf', (err, data) => {
    if (err) {
        console.error('Error reading file:', err.message);
        return;
    }
    // This runs only when the OS finishes the heavy lifting
    console.log(`3. Success! Processed ${data.length} bytes.`);
});

// This executes while the file is still being read by the OS
console.log('2. Main thread is free! Handling other user requests...');

/* 
 * Package: io.thecodeforge.node.web
 */
const http = require('http');

const PORT = process.env.PORT || 3000;

const server = http.createServer((req, res) => {
    const { method, url } = req;

    // Standard REST routing logic
    if (method === 'GET' && url === '/') {
        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ 
            status: 'success', 
            message: 'Welcome to TheCodeForge API' 
        }));

    } else if (method === 'GET' && url === '/health') {
        res.writeHead(200, { 'Content-Type': 'text/plain' });
        res.end('UP');

    } else {
        res.writeHead(404, { 'Content-Type': 'application/json' });
        res.end(JSON.stringify({ error: 'Endpoint Not Found' }));
    }
});

server.listen(PORT, () => {
    console.log(`[TheCodeForge] Server ignited on port ${PORT}`);
});

/* 
 * Package: io.thecodeforge.node.modules
 */

// --- CommonJS (Standard in older Node apps) ---
// utils.js -> module.exports = { log: (msg) => console.log(msg) };
// app.js   -> const { log } = require('./utils');

// --- ES Modules (Recommended for new projects) ---
// In package.json, set "type": "module"

import os from 'os';
import { networkInterfaces } from 'os';

const systemMetrics = {
    platform: os.platform(),
    freeMem: (os.freemem() / 1024 / 1024 / 1024).toFixed(2) + ' GB',
    uptime: (os.uptime() / 3600).toFixed(1) + ' hours'
};

console.log('System Status:', systemMetrics);

# Initialize a new project
npm init -y

# Install a package as a production dependency
npm install express

# Install as dev dependency
npm install --save-dev nodemon

# Run a script defined in package.json
npm run start

# List outdated packages
npm outdated

# Update all packages (respects semver)
npm update

/* 
 * Package: io.thecodeforge.node.eventloop
 */
const fs = require('fs');
const crypto = require('crypto');

console.log('1. Main script start');

setTimeout(() => console.log('5. Timer phase'), 0);

setImmediate(() => console.log('6. Check phase (setImmediate)'));

process.nextTick(() => console.log('3. nextTick queue'));

Promise.resolve().then(() => console.log('4. Microtask queue (Promise)'));

fs.readFile('dummy.txt', () => {
    console.log('7. I/O callback (poll phase)');
    process.nextTick(() => console.log('8. nextTick inside I/O'));
    setImmediate(() => console.log('9. setImmediate inside I/O'));
});

console.log('2. Main script end');