What are common use cases of closures?

Short answer: Data privacy / encapsulation Callbacks and event handlers Memoization / caching Module pattern for structuring code Example – private counter: function createCounter() { let count = 0; // private variable

Example code

return { increment: () => ++count, decrement: () => --count }; }
const counter = createCounter(); console.log(counter.increment()); // 1 console.log(counter.decrement()); // 0

Real-world example (ShopNest)

In ShopNest’s cart UI, a click handler closes over productId. Use let in loops so each button keeps the correct id.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.