React Interview Preparation Guide

22+ Q&A covering React hooks, component patterns, performance, state management, forms, testing, and internals

Topics

Hooks

File	Topics	Difficulty
useState	State initialization, functional updates, lazy init	🟢
useEffect	Side effects, cleanup, dependency array	🟡
useContext & useReducer	Context API, complex state, dispatch patterns	🟡
useCallback & useMemo	Memoization, referential equality, performance	🟡
useRef	DOM access, mutable values, timers	🟢
useReducer	Reducer pattern, complex state transitions	🟡
Custom Hooks	Encapsulating logic, common patterns	🟡

Component Patterns

File	Topics	Difficulty
Composition	Children, render props, slots, inversion of control	🟡
HOC	Higher-order components, when to avoid	🟡
Render Props	Function-as-child, when to use vs hooks	🟡
Error Boundaries	Catching errors, fallback UI, React 18	🟡
Code Splitting	React.lazy, Suspense, route splitting	🟡

Internals & Rendering

File	Topics	Difficulty
Virtual DOM & Reconciliation	Diffing, keys, commit phase	🟡
Fiber Architecture	Concurrent rendering, time-slicing, priority	🔴
Rendering Optimization	React.memo, profiling, avoid re-renders	🟡
Component Basics	Functional vs class, JSX, createElement	🟢
Lifecycle Methods	Mount/update/unmount, hooks equivalent	🟡

State Management

File	Topics	Difficulty
State Management	State vs props, lifting state, local vs global	🟡
Context API	Performance pitfalls, splitting contexts	🟡
Redux & Zustand	Store patterns, selectors, when to use	🟡
Concurrent Features	useTransition, useDeferredValue, batching	🔴

Data & Forms

File	Topics	Difficulty
Forms	Controlled vs uncontrolled, React Hook Form	🟡
Events	Synthetic event system, delegation, cleanup	🟡
Suspense & Data Fetching	Boundary architecture, transitions	🔴
SSR	Hydration, renderToPipeableStream, CSR vs SSR	🔴
Server Components	RSC, App Router, zero bundle	🔴

Quality & Tooling

File	Topics	Difficulty
Testing	React Testing Library, accessible queries, mocking	🟡
TypeScript	Props typing, generics, utility types	🟡
Security	XSS, CSRF, token storage, CSP	🟡
Styling	CSS Modules, CSS-in-JS, Tailwind, performance	🟢
Routing	React Router v6, protected routes, auth	🟡
Performance	Code splitting, Profiler, metrics	🟡

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Most Frequently Asked

1. useState & useEffect fundamentals (⭐⭐⭐⭐⭐)
2. Component re-rendering mechanics (⭐⭐⭐⭐⭐)
3. useCallback vs useMemo (⭐⭐⭐⭐)
4. Context API patterns (⭐⭐⭐⭐)
5. React.memo optimization (⭐⭐⭐⭐)

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Content from Frontend-Master-Prep-Series — 03-react