React Interview Questions With AI-Powered Feedback

Frontend interviews cover: React hooks (useState, useEffect, useCallback, useMemo, useRef, custom hooks), reconciliation and the virtual DOM, component design patterns, performance optimization (React.memo, lazy loading, code splitting), state management (Context API, Redux, Zustand), and error boundaries. For senior roles, interviewers also test React architecture decisions and tradeoff reasoning.

useMemo memoizes the result of an expensive computation and returns the cached value on subsequent renders when dependencies haven't changed. useCallback memoizes a function reference so it stays stable across renders. Use useMemo for expensive calculations; use useCallback when passing callbacks to child components that rely on referential equality to skip re-renders.

React reconciliation is the process by which React updates the DOM. When state or props change, React creates a new virtual DOM tree and compares it to the previous tree using a diffing algorithm. React assumes elements of different types produce different trees, and uses the 'key' prop to identify list items. React Fiber (introduced in React 16) broke this work into units that can be paused and prioritized.

Prepare by: (1) Understanding how each hook works internally, not just how to use it; (2) Building custom hooks for real use cases (debounce, fetch, local storage); (3) Practicing machine coding — build components like autocomplete, infinite scroll, and drag-and-drop; (4) Understanding React performance patterns — when and why to use React.memo, useMemo, and lazy; (5) Getting AI feedback on your answers to identify weak spots.