I put together a list of React problems I kept seeing come up in interview prep — mix of core hooks, a couple of classic "build this component" asks, and a few that companies like Meta/Airbnb/Flipkart actually use. Figured I'd share instead of just keeping the list to myself.

Didn't want to just describe them — you can open each one and actually write + run the code against real tests in the browser, no setup. Links go straight to the problem.

1. Build a counter with three buttons. The classic warm-up — but the interesting part is making sure rapid clicks never lose an update.

Practice counter problem

2. Delay a value until the user stops typing. You've used this in every search box you've ever built — now write the hook yourself.

Practice this problem

1. Track what a value used to be, one render ago. Small hook, but people trip over when it actually updates.

Practice usePrevious hook

1. Model a shopping cart's add/remove/update-quantity logic. A good test of whether you reach for useReducer or keep fighting with useState.

Create shopping cart

1. Build a traffic light that cycles red → green → yellow on its own timer. Looks simple until you have to get the timing and cleanup exactly right.

Create traffic light

6. Build a search box where slow responses can't overwrite fast ones. This is the one that trips almost everyone up the first time — asked at Airbnb.

Create search box

7. Render a comment thread with infinite nested replies. Recursion inside JSX — asked at Meta.

Build nested comment

8. Stop a long list from re-rendering every item on every keystroke elsewhere on the page. A real performance debugging exercise, not just a memo() one-liner.

Practice memoization

9. Give a callback prop a stable identity across renders. Sounds trivial, isn't — especially once a child component is memoized.

Stable callback

10. Build a modal where keyboard focus can't escape it. Accessibility question that separates "I use libraries" from "I understand the DOM."

Practice this problem

11. Write a fetch hook that won't re-request data it already has. Basically: build a tiny cache layer from scratch.

Build usecatche

12. Manage state for a multi-step form wizard. Back/next/jump-to-step, without the state turning into spaghetti.

Multi-step form

13. Build an autocomplete search with keyboard-navigable suggestions. Filtering logic plus a surprisingly fiddly amount of UI state.

React auto-complete practice

14. Add undo/redo to a stateful app. Command-pattern state history — the kind of thing that's easy to describe and annoying to actually implement cleanly.

Undo/Redo Functionality

15. Build a month calendar grid that handles real date math. Leap years, month boundaries, the works — asked at Flipkart.

Build calendar grid