What is the difference between var, let, and const?

Short answer: var: function-scoped, can be redeclared. let: block-scoped, cannot redeclare in the same scope. const: block-scoped, cannot be reassigned. Example: var x = 10; let y = 20; const z = 30;

Example code

var: function-scoped, can be redeclared. let: block-scoped, cannot redeclare in the same scope. const: block-scoped, cannot be reassigned. Example: var x = 10;
let y = 20;
const z = 30;

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.