What is block scope?

Short answer: Variables declared with let or const inside curly braces {} are accessible only within that block. Example: if (true) { let y = 20; const z = 30; } // console.log(y, z); // ReferenceError

Example code

Variables declared with let or const inside curly braces {} are accessible only within that block. Example: if (true) {
let y = 20;
const z = 30;
} // console.log(y, z); // ReferenceError

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.