Frontend Developer Interview Questions Quiz – Junior & Mid Level

Practice with real frontend interview questions. Type your answers, get instant feedback, and check if you’re ready for your next job.

Part 1

Question 1: How can you optimize performance in a React application with large tables or data sets?

Question 2: What is the main challenge in optimizing React applications with large datasets?

Question 3: Why is preventing memory leaks crucial in React applications?

Question 4: How important is TypeScript in modern frontend projects?

Question 5: How can you assess your TypeScript knowledge level?

Question 6: What TypeScript topics should be learned beyond the basics?

Question 7: How does the Omit utility type work in TypeScript?

Question 8: What are conditional types in TypeScript?

Question 9: How is the infer keyword used in TypeScript?

Question 10: What are the benefits of using TypeScript in development?

Part 2

Question 11: What are common TypeScript anti-patterns?

Question 12: How should any, unknown, and never be used properly in TypeScript?

Question 13: Why can 'as' be dangerous in TypeScript?

Question 14: When should Server-Side Rendering (SSR) be used?

Question 15: When is SSR not appropriate?

Question 16: What are effective frontend optimization techniques?

Question 17: Why use virtualization (react-window / react-virtualized) for lists?

Question 18: What is lazy loading of components and how does it work?

Question 19: How to handle unnecessary re-renders in React apps?

Question 20: What’s the difference between React.memo and useCallback?

Part 3

Question 21: How to prevent child components from re-rendering if props haven’t changed?

Question 22: What is the purpose of Code Review?

Question 23: What actions help with SEO optimization?

Question 24: What are Open Graph tags and why use them?

Question 25: What role do tests play in frontend development?

Question 26: What are End-to-End (E2E) tests and what do they check?

Question 27: Why don’t unit tests replace E2E and vice versa?

Question 28: When is it not advisable to write tests?

Question 29: How to test React components?

Question 30: What is useEffect and when is it used?

Part 4

Question 31: How to safely use event listeners in useEffect?

Question 32: How to persist the state of a modal window across sessions?

Question 33: How to handle an array of Promises and return the first resolved value or all errors?

Question 34: How to group numbers by their digit composition, regardless of order?

Question 35: What is the time complexity of digit-grouping logic?

Question 36: What tools help identify performance bottlenecks in React applications?

Question 37: What approaches are used to memoize objects and arrays in React?

Question 38: What is the difference between using localStorage and server storage for persisting modal state?

Question 39: What role do template literal types play in TypeScript?

Question 40: What are mapped types used for in TypeScript?

Part 5

Question 41: What does the keyof operator do in TypeScript?

Question 42: How does type restriction with extends work in TypeScript?

Question 43: Why is it important to use type guards with unknown in TypeScript?

Question 44: What is the risk of overusing @ts-ignore in TypeScript?

Question 45: What practices improve website SEO visibility besides SSR?

Question 46: How does Code Review support knowledge sharing within a team?

Question 47: What test paths are critical even in prototypes or MVPs?

Question 48: Why is cleanup-return needed in useEffect with subscriptions or event listeners?

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