Path 12: EventEmitter aur Streams

Node.js me events module ka EventEmitter class publish-subscribe pattern deta hai. Koi emit karta hai, koi on se sunta hai. Isi pattern par streams bhi chalti hain — data, end aur error events.

1. Chhota example

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

bus.on('tick', (msg) => {
  console.log('mila:', msg);
});

bus.emit('tick', { n: 1 });

2. Stream se padhna

const fs = require('fs');
const rs = fs.createReadStream('notes.txt', 'utf8');

rs.on('data', (chunk) => process.stdout.write(chunk));
rs.on('end', () => console.log('\nkhatm'));
rs.on('error', (e) => console.error('galti:', e.message));

3. Yaad rakhne wali baatein

Pehle on lagao, phir emit karo — ulta karne par event kho jata hai. error event ka listener hamesha lagao, warna process crash ho sakta hai.