02 Core Modules

Node.js ke paas pehle se bane hue kaafi tools (Modules) hain jo hamara kaam aasaan karte hain. Inhe use karne ke liye humein kuch install nahi karna padta, bas require ya import karna hota hai.

1. File System (fs) 📂

Files ke sath kaam karne ke liye (Read, Write, Delete) fs module use hota hai.

Read a File

const fs = require('fs');

// Asynchronous (Recommended)
fs.readFile('hello.txt', 'utf8', (err, data) => {
  if (err) {
    console.error(err);
    return;
  }
  console.log(data);
});

Write a File

const content = "Aaj humne Node.js seekha!";
fs.writeFile('notes.txt', content, err => {
  if (err) {
    console.error(err);
  } else {
    // File written successfully
  }
});

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2. Path Module (path) 🛣️

Alag-alag Operating Systems (Windows vs Mac) me paths alag tarike se likhe jate hain (Example: \ vs /). path module is problem ko solve karta hai.

const path = require('path');

// Join Paths (Safe for all OS)
const filePath = path.join(__dirname, 'docs', 'file.txt');
console.log(filePath);
// Output: /Users/adi/project/docs/file.txt (Mac)
// Output: C:\Users\adi\project\docs\file.txt (Windows)

// Extension nikalna
console.log(path.extname('image.png')); // .png

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3. OS Module (os) 💻

Operating System ki information lene ke liye.

const os = require('os');

console.log("Platform:", os.platform()); // 'darwin' (Mac) or 'win32' (Windows)
console.log("CPU Architecture:", os.arch()); // 'x64' or 'arm64'
console.log("Free Memory:", os.freemem()); // Bytes me

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4. HTTP Module (http) 🌐

Apna khud ka web server banane ke liye! (Lekin production me hum aksar Express use karte hain jo iske upar bana hai).

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === '/') {
    res.write('Namaste Node.js World! 🙏');
    res.end();
  } else if (req.url === '/about') {
    res.write('Ye ek simple server hai.');
    res.end();
  }
});

server.listen(3000, () => {
  console.log('Server running on port 3000...');
});

---

5. Events Module (events) 📢

Node.js Event-Driven hai. Aap apne custom events bana sakte hain aur unhe sun (listen) sakte hain.

const EventEmitter = require('events');
const myEmitter = new EventEmitter();

// Event Listener (Intezaar kar raha hai)
myEmitter.on('login', (username) => {
  console.log(`Welcome back, ${username}! 🎉`);
});

// Event Trigger (Event fire kiya)
myEmitter.emit('login', 'Aditya');

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Summary

Ye modules Node.js ki “Toolkit” hain.

• fs: Files ke liye.
• path: Paths handle karne ke liye.
• os: System info ke liye.
• http: Server banane ke liye.
• events: Custom events ke liye.

Next Up: Ab hum banayenge apna pehla proper backend server using PRO tool: Express.js! 🚀