Factory Pattern creates objects without the client knowing the creation logic. Client says "give me a Circle", factory handles the "new Circle(radius, color, ...)". Useful when object creation is complex or varies by type.

🏭Build a Notification Factorymedium

Step 1/5

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The Problem — Notification Sprawl

Identifying the Need for a Pattern

You're building a notification system for an e-commerce platform. Right now it only sends emails. But the product team wants SMS for order updates and push notifications for promotions. The current code has if-else chains everywhere to decide which notification to send.

Code

function sendNotification(type: string, to: string, msg: string) {
  if (type === 'email') {
    const smtp = new SmtpClient()
    smtp.connect('smtp.gmail.com')
    smtp.send({ to, subject: 'Notification', body: msg })
    smtp.disconnect()
  } else if (type === 'sms') {
    const twilio = new TwilioClient(API_KEY)
    twilio.messages.create({ to, body: msg })
  } else if (type === 'push') {
    const firebase = new FirebaseAdmin()
    firebase.messaging().send({ token: to, body: msg })
  }
  // TODO: Slack, WhatsApp, in-app...
}

Question

What's the core problem with this approach?

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LLD|🎨 Additional Patterns| 20 min

Factory Pattern

Intermediate20 min read+10 XP

TL;DR — Factory Pattern

Learn Factory Pattern — a key concept for LLD interviews.

Interactive — Try it yourself!

How to use

1Select "Factory" tab in the Pattern Playground

2Click Margherita/Pepperoni/Hawaiian to create pizzas

3Watch: Factory creates the right subclass without you calling new()

4Notice: Client just says WHAT, Factory handles HOW

In a nutshell