Frontend React Screen

Frontend phone screen covering React fundamentals, CSS concepts, UI troubleshooting, component structure, and sometimes a coding warm-up such as merge intervals or debounce. Requirements Prepare for a frontend screen covering both coding and verbal React concepts. Coding: Merge intervals. Write a debounce function. Discuss time and space complexity. React / frontend concepts: What is the Virtual DOM? How does the Virtual DOM help React? Which hooks have you used and why? What changed in React 18 concurrent features? Server components vs client components. How do you handle errors in React? Core CSS concepts. How you diagnose UI issues and structure components. Notes For debounce, define leading vs trailing behavior and cancellation. For React, answer from execution model rather than slogans: rendering, reconciliation, scheduling, hydration, server/client boundary, and error boundaries. For the newer full-stack screen variant, also be ready to explain CSS fundamentals, how you isolate UI bugs, and how you split a UI into maintainable components. Preparation Implement debounce(fn, delay) with cancel() and optional leading invocation. Solve merge intervals quickly so the round can move into frontend depth. Prepare concise examples for useEffect, useMemo, useCallback, useRef, and custom hooks. Review error boundaries and what they do not catch.