const in React — React Technical Interview Questions & Answers

const in React

const in React

  • const means the binding doesn’t get reassigned. Components are usually const Box = () => …. useState’s setter is const setN = … — you call setN(1), you don’t do setN = otherFn. const does not make the value on screen frozen; state still updates via the setter.
  • let is fine for loop indexes outside JSX. Prefer const by default. Don’t confuse const with React.memo or Object.freeze.
  • const in React — box and setN are const. Click still works — we call setN, we don’t do setN = something else.

Technical Interview Tip: const component + setter still updates UI.

Code Examples for const in React

Example

// const
import { useState } from "react";

const Box = () => {
  const [n, setN] = useState(0);
  return <button onClick={() => setN(n + 1)}>{n}</button>;
};

export default Box;

const in React — box and setN are const. Click still works — we call setN, we don’t do setN = something else.

How to Explain const in React to an Interviewer

Explain const as if you are teaching a junior — definition, then one tiny UI.

const : no rebinding. setState : call, don’t reassign.

Write 5–10 lines that use const and say what the UI does.

Show JSX Say the screen

What mistake do freshers make with const?

‘const means UI can’t change’.