Top 8 Frontend Development Interview Questions
Frontend engineering interview questions used by European tech companies. React, TypeScript, performance optimization, and accessibility — key skills for roles at Booking.com, Wise, and N26.
Explain the React component lifecycle and hooks equivalents.
Expert Tip: useEffect covers mount/update/unmount. Discuss cleanup and dependency arrays.
How would you optimize a React application that renders 10,000 items?
Expert Tip: Virtualization (react-window), pagination, memo, useMemo, useCallback.
Explain the event loop in JavaScript.
Expert Tip: Call stack, task queue, microtask queue, requestAnimationFrame. Order matters!
How does SSR differ from SSG in Next.js? When would you use each?
Expert Tip: SSR: dynamic data per request. SSG: build-time. ISR: best of both.
Design a reusable form component that handles validation in 5 languages.
Expert Tip: Discuss i18n patterns, Zod/Yup, react-hook-form, and locale-aware messages.
What is a closure? Provide a practical example.
Expert Tip: Functions that capture variables from outer scope. useState implementation is a closure.
How would you implement dark mode across a large application?
Expert Tip: CSS custom properties, system preference detection, tailwind dark: prefix.
Explain Web Vitals (LCP, FID, CLS) and how to optimize each.
Expert Tip: Google ranking factor. Image optimization, code splitting, font display swap.
Recommended Resources
javascript.info
Deep dive into JavaScript fundamentals.
Kent C. Dodds blog
React patterns and testing best practices.
web.dev
Google's Web Vitals and performance guides.