A hiring manager's question bank for React developers — hooks, state, rendering and reconciliation, performance, and component design. Built to separate people who can wire up a component from people who understand why it re-renders.
Modern React looks simple on the surface — write a function, return some JSX, sprinkle in a hook — but the developers who are worth hiring are the ones who understand what React is doing underneath. Most real React problems are not "how do I show this data?" but "why is this re-rendering forty times?", "why does this effect run twice?", or "why is my state one update behind?". So a good interview probes mental models, not API recall. A strong candidate can explain why state updates are batched and asynchronous, what actually goes in a useEffect dependency array and why, the difference between derived state and stored state, and when memoization genuinely helps versus when it just adds noise. The questions below progress from hooks and state through rendering and reconciliation into performance and component design, which is roughly the order in which seniority reveals itself. You are listening for someone who thinks in terms of data flow and render cycles, who knows when to lift state up and when not to, and who can explain a tradeoff like "I reached for context here, but it would have caused unnecessary re-renders, so I did this instead." Pair a couple of hook questions with one rendering scenario and one component-design discussion, and you will quickly tell whether someone has maintained a real React codebase or only followed tutorials.
Choose six to eight questions across two or three categories instead of running the full list. Open with a Hooks & State question, move into a Rendering & Reconciliation scenario, then close on a Component Design discussion. Push every clean answer with "what triggers a re-render here?" or "when would that hurt performance?" — the follow-up is where real React understanding shows.
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