Fundamentals

Fundamentals Questions

Q1.How does React Native differ from React for web?+

React Native uses native components instead of HTML DOM — View instead of div, Text instead of p, Image instead of img. Styling uses StyleSheet API (similar to CSS but not identical — Flexbox for layout, no CSS Grid). Navigation uses React Navigation instead of React Router. There is no browser API — native APIs replace localStorage, fetch works similarly.

Q2.What is the bridge architecture in React Native?+

The traditional React Native architecture had three threads: JavaScript thread (runs your code), main/UI thread (renders native components), and shadow thread (calculates layout). The bridge serialized data between JS and native as JSON messages. The new architecture (Fabric, TurboModules, JSI) replaces the bridge with direct JavaScript-to-native communication for better performance.

Q3.Explain the difference between Expo and React Native CLI.+

Expo provides a managed workflow with pre-configured native modules, over-the-air updates, and easy build/submit tools (EAS). React Native CLI gives full native control but requires Xcode/Android Studio setup. Start with Expo — use development builds (expo-dev-client) when you need custom native modules. Eject only if absolutely necessary.

Q4.How does React Native handle platform-specific code?+

Three approaches: Platform.OS checks ('ios'/'android') for conditional logic, Platform.select({ios: ..., android: ...}) for platform-specific values, and platform-specific files (Component.ios.tsx, Component.android.tsx) for entirely different implementations. Use platform files for large differences and Platform.OS for small tweaks.

Q5.What is Hermes and why is it used in React Native?+

Hermes is a JavaScript engine optimized for React Native. It precompiles JavaScript to bytecode at build time, reducing app startup time by 30-50%, reducing memory usage by 20-30%, and decreasing app binary size. It is enabled by default in new React Native projects and is the recommended engine for production apps.

Framework-Specific

Framework-Specific Questions

Q6.How does React Navigation work in React Native?+

React Navigation provides a JavaScript-based navigation solution. Stack navigator: push/pop screens (like browser history). Tab navigator: bottom or top tab bars. Drawer navigator: side drawer menu. Navigators can be nested. Navigation state is managed as a tree of screens. Use useNavigation hook for programmatic navigation and route params for passing data between screens.

Q7.How do you handle state management in React Native?+

Small apps: useState + useContext. Medium apps: Zustand (simple, minimal boilerplate). Large apps: Redux Toolkit (predictable state with DevTools). For server state: TanStack Query (API caching, refetching). For persistent local state: AsyncStorage or MMKV (faster). Choose based on app complexity — avoid Redux for simple apps.

Q8.Explain FlatList optimization techniques.+

FlatList renders items lazily (only visible items). Optimize with: getItemLayout (skip layout calculation for fixed-height items), keyExtractor (stable unique keys), React.memo on renderItem components, windowSize adjustment (default 21 — reduce for less memory), removeClippedSubviews on Android, and maxToRenderPerBatch for controlling render chunks.

Q9.How do you implement push notifications in React Native?+

Use expo-notifications with Expo or react-native-firebase for bare workflow. Register device token on app launch, send token to your server. Server sends notifications via Expo Push API or Firebase Cloud Messaging. Handle notification received (foreground), notification tapped (background/killed), and navigate to relevant screen based on notification data.

Q10.What are native modules in React Native?+

Native modules bridge React Native JavaScript code to platform-specific native code (Java/Kotlin for Android, Swift/Objective-C for iOS). Use when you need functionality not available in JavaScript — accessing device sensors, custom camera features, or integrating native SDKs. With the new architecture (TurboModules), native modules load lazily and communicate more efficiently.

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Project / Practical

Project / Practical Questions

Q11.How would you implement offline support in a React Native app?+

Use NetInfo to detect connectivity. Cache API responses with AsyncStorage or MMKV. Queue mutations when offline (optimistic updates). Sync queued mutations when connectivity returns. Use WatermelonDB for complex offline-first data with SQLite. Show offline indicator to users and handle conflicts with last-write-wins or user resolution.

Q12.Describe your approach to handling images efficiently in React Native.+

Use FastImage (or expo-image) for caching and progressive loading. Resize images on the server to match display dimensions. Use WebP format for smaller sizes. Implement lazy loading for lists. Set resizeMode appropriately. For user uploads, compress before uploading with react-native-image-picker compression options.

Q13.How do you debug a React Native application?+

Use React Native DevTools (Flipper or new JS debugger). Console.log for quick checks. React DevTools for component inspection. Chrome DevTools for network requests. For native crashes: Android Studio Logcat (Android) or Xcode console (iOS). Performance: use React DevTools Profiler and Systrace. In production: Sentry or Bugsnag for crash reporting.

Problem Solving

Problem Solving Questions

Q16.How would you optimize a React Native app that has slow animations?+

Move animations off the JS thread using react-native-reanimated (runs on UI thread). Replace JavaScript-driven animations with native driver (useNativeDriver: true for Animated API). Reduce re-renders with React.memo and useCallback. Avoid heavy computation during animations. Profile with Systrace to identify JS thread bottlenecks.

Q17.How would you implement biometric authentication in a React Native app?+

Use expo-local-authentication or react-native-biometrics. Check device support with hasHardwareAsync() and isEnrolledAsync(). Prompt authentication with authenticateAsync(). Store sensitive data (tokens) in Keychain (iOS) or Keystore (Android) using expo-secure-store. Provide PIN fallback for devices without biometric hardware.

Frequently Asked Questions

Common Questions

What topics are asked in React Native interviews?+

React fundamentals, React Native core components, navigation, state management, native modules, performance optimization, and app store deployment. Companies also test JavaScript/TypeScript fundamentals.

Are React Native interviews harder than React web interviews?+

They cover additional mobile-specific topics (navigation, native modules, platform differences) on top of React knowledge. If you know React well, the mobile-specific additions are manageable.

Does CodingClave prepare students for React Native interviews?+

Yes. The 6-month React Native program at CodingClave in Lucknow includes mock interviews covering mobile development concepts and practical project demonstrations.

Should I learn native development (Swift/Kotlin) for React Native interviews?+

Basic understanding helps. You do not need to be proficient, but knowing how to bridge native modules and debug platform-specific issues is valued.

What salary can I expect after clearing a React Native interview?+

₹3.5-8 LPA for freshers. In Lucknow, ₹4-6.5 LPA. Remote mobile development roles pay ₹7-15 LPA.

How important is a published app for React Native interviews?+

Very. A live app on the Play Store or App Store demonstrates real-world experience. It shows you understand the full lifecycle from development to submission.

Is Expo knowledge sufficient for interviews?+

For most companies, yes. Expo covers 90% of use cases. Understanding when and how to eject to bare workflow and work with native modules is a bonus that sets you apart.

Can React Native interview prep help for React web interviews?+

Yes. The React core (hooks, state, component patterns) is identical. Your mobile knowledge adds versatility that web-only candidates lack.

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React Native Interview Questions and Answers 2026

Top 15 React Native interview questions with answers. Mobile app development, navigation, and native modules questions for freshers.