Interview practice by role
React Developer Interview Practice
React interviews go past syntax into how rendering, effects and state actually behave. Interviewers ask why something re-renders, why an effect runs twice and when memoisation helps or hurts.
160 practice questions4 topics5 typical rounds
How the interview usually runs
Loops differ by company. Treat this as a common pattern, not a fixed format.
- 01Screening callYour React experience, the size of the apps you worked on and your testing habits.
- 02React fundamentalsComponents, props, state, keys, controlled inputs and the rendering model.
- 03Hooks and performanceuseEffect dependencies, stale closures, custom hooks, memoisation and avoiding unnecessary renders.
- 04Live codingBuild a feature such as a searchable list or a form with validation, then refactor it with the interviewer.
- 05Architecture discussionState management choices, code splitting, data fetching and how you structure a large codebase.
What interviewers probe
- What triggers a render and what the reconciliation step does
- Effect dependencies, cleanup and common stale-state bugs
- When to lift state, use context or reach for a store
- Memoisation trade-offs: useMemo, useCallback and React.memo
- Testing components by behaviour rather than implementation
Common mistakes
- Saying useMemo makes things faster without naming the cost it avoids
- Treating useEffect as a lifecycle method instead of a synchronisation tool
- Not explaining the trade-off when choosing a state library
Practice questions for React Developer interviews
A starting set from each topic. Every question has a short answer, the full reasoning and the follow-ups interviewers ask.
01How does the virtual DOM and reconciliation work?Mediumvirtual DOM · reconciliation · rendering02Why is React state described as a snapshot?Mediumstate · rendering · closures03What is state batching in React?Mediumstate · batching · rendering04What is a closure in JavaScript?Mediumscope · lexical environment · functions05How does this work in JavaScript?Mediumthis · functions · call site06What is hoisting in JavaScript?Mediumhoisting · scope · execution context07What is the difference between interfaces and type aliases?Mediuminterfaces · type-aliases · declaration-merging08What are intersection types?Mediumintersections · composition · type-system09How do enums work and when should you use them?Mediumenums · runtime · state10How does CSS specificity work?Mediumspecificity · selectors · cascade11Explain the position property and its values.Mediumposition · containing block · layout12How does Flexbox work?Mediumflexbox · layout · alignment
Reading is step one
Now say it out loud.
Understanding an answer and delivering it under pressure are different skills. Rehearse this topic in a live React Developer mock interview and get scored feedback on depth, clarity and confidence.