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React Native Interview Questions & Answers

Q1. What is React Native?

Fresher
React Native is an open-source framework by Facebook for building mobile applications using JavaScript and React, allowing development for both iOS and Android.

Q2. What is the difference between React and React Native?

Fresher
React is used for building web applications, while React Native is for mobile apps. React Native uses native components instead of HTML elements.

Q3. What programming language is used in React Native?

Fresher
React Native uses JavaScript and optionally TypeScript to build cross-platform mobile applications.

Q4. What is a component in React Native?

Fresher
A component is a reusable building block in React Native that defines a part of the UI. Components can be class-based or functional.

Q5. What is the difference between state and props in React Native?

Fresher
Props are read-only properties passed to a component, while state is mutable data managed within a component that can change over time.

Q6. What are the types of components in React Native?

Fresher
There are two main types: Functional Components, which are functions returning JSX, and Class Components, which extend React.Component.

Q7. What is JSX in React Native?

Fresher
JSX is a syntax extension for JavaScript that looks like HTML, allowing developers to write UI code inside JavaScript functions.

Q8. What is the role of the render() method in React Native?

Fresher
The render() method returns the JSX describing what should be displayed on the screen for class components.

Q9. What is the difference between ScrollView and FlatList?

Fresher
ScrollView renders all child components at once, suitable for small lists. FlatList renders items lazily, improving performance for large lists.

Q10. What is a virtual DOM in React Native?

Fresher
The virtual DOM is an in-memory representation of the UI that React uses to efficiently update the real UI by diffing changes.

Q11. What is the difference between controlled and uncontrolled components?

Fresher
Controlled components have their value managed by React state, while uncontrolled components manage their own internal state.

Q12. What is the purpose of StyleSheet in React Native?

Fresher
StyleSheet is used to define styles for components in a structured and performance-optimized way, similar to CSS.

Q13. What is the difference between TouchableOpacity and TouchableHighlight?

Fresher
TouchableOpacity reduces the opacity of the component when pressed, while TouchableHighlight darkens the background color.

Q14. What is the difference between React Native and Flutter?

Fresher
React Native uses JavaScript and bridges to native components, while Flutter uses Dart and its own rendering engine to build UI.

Q15. What is the difference between stateful and stateless components?

Fresher
Stateful components manage internal state and can re-render, while stateless components rely on props and do not manage state.

Q16. What is the difference between props drilling and context API?

Fresher
Props drilling passes data through multiple levels, while context API allows sharing data globally without passing through each component.

Q17. What is React Navigation?

Fresher
React Navigation is a library for handling routing and navigation in React Native apps, including stack, tab, and drawer navigation.

Q18. What is the difference between componentDidMount and useEffect?

Fresher
componentDidMount is used in class components for initialization, while useEffect performs side effects in functional components.

Q19. What is the difference between state and Redux store?

Fresher
State is local to a component, while Redux store holds global state that can be accessed and updated across the entire app.

Q20. What is a key in React Native and why is it important?

Fresher
Keys uniquely identify elements in a list to help React optimize re-rendering and maintain component state correctly.

Q21. What is the difference between Native Modules and Native Components?

Fresher
Native Modules provide platform-specific functionality to JS code, while Native Components render UI elements directly on the native platform.

Q22. What is the difference between Expo and React Native CLI?

Fresher
Expo provides an easy-to-use environment with built-in tools and libraries, while React Native CLI offers full native project control.

Q23. What is the purpose of useState hook?

Fresher
useState hook allows functional components to have state variables and update them, triggering a re-render when state changes.

Q24. What is the purpose of useEffect hook?

Fresher
useEffect hook performs side effects like data fetching, subscriptions, or manual DOM updates in functional components.

Q25. What is the difference between PureComponent and Component?

Fresher
PureComponent implements a shallow comparison to prevent unnecessary re-renders, while Component does not implement this optimization.

Q26. What is the difference between React Native and Ionic?

Fresher
React Native renders native UI components for performance, while Ionic uses web technologies inside a WebView, which may impact performance.

Q27. What is a Fragment in React Native?

Fresher
Fragment is a wrapper that allows grouping multiple elements without adding extra nodes to the UI tree.

Q28. What is the difference between inline and external styling?

Fresher
Inline styling is defined directly in JSX, while external styling uses StyleSheet or separate files for better organization and performance.

Q29. What is the difference between controlled and uncontrolled TextInput?

Fresher
Controlled TextInput manages its value via React state, while uncontrolled TextInput maintains its own internal value.

Q30. What is hot reload in React Native?

Fresher
Hot reload updates the app’s UI instantly without losing its state, speeding up development and testing.

Q31. What is the difference between React Native CLI and Expo?

Intermediate
React Native CLI provides full control over native code, while Expo offers a managed workflow with pre-built libraries, faster setup, and easier testing.

Q32. What are React Native hooks and their importance?

Intermediate
Hooks like useState, useEffect, useReducer, and useContext allow functional components to manage state, lifecycle methods, and context efficiently.

Q33. What is the difference between useState and useReducer?

Intermediate
useState is for simple state management, while useReducer is suited for complex state logic with multiple actions and state transitions.

Q34. What is Context API in React Native?

Intermediate
Context API allows sharing state across components globally without props drilling, making it easier to manage app-wide data like themes or authentication.

Q35. What is Redux and why is it used in React Native?

Intermediate
Redux is a predictable state container that centralizes app state, making state management easier in complex apps with multiple components.

Q36. What is the difference between Redux and MobX?

Intermediate
Redux uses a single immutable store with strict state updates, while MobX uses observable states with reactive updates, offering simpler and more flexible patterns.

Q37. What is the difference between React Navigation v4 and v5?

Intermediate
v4 uses a static configuration for routes, while v5 introduces a dynamic, component-based API with better flexibility, deep linking, and type safety.

Q38. What are performance optimization techniques in React Native?

Intermediate
Techniques include using PureComponent, memoization, FlatList for large lists, avoiding unnecessary re-renders, lazy loading, and optimizing images.

Q39. What is the difference between FlatList, SectionList, and ScrollView?

Intermediate
FlatList renders a large list efficiently, SectionList adds section headers, and ScrollView renders all content at once, suitable for small scrollable areas.

Q40. What is the difference between TouchableOpacity, TouchableHighlight, and Pressable?

Intermediate
TouchableOpacity changes opacity on press, TouchableHighlight adds a background color effect, and Pressable provides advanced gesture and state handling.

Q41. What is the difference between Class and Functional Components?

Intermediate
Class components use lifecycle methods and state, while functional components are simpler and use hooks for state and side effects.

Q42. What is the difference between componentDidMount and useEffect?

Intermediate
componentDidMount runs after class components mount, while useEffect with an empty dependency array runs once after functional components mount.

Q43. What is the difference between native modules and native components?

Intermediate
Native modules expose platform-specific functionalities to JS, while native components render UI elements directly on the native platform.

Q44. What is the difference between controlled and uncontrolled components?

Intermediate
Controlled components have values managed by React state, while uncontrolled components manage their own internal state.

Q45. What are higher-order components (HOCs) in React Native?

Intermediate
HOCs are functions that take a component and return a new component with enhanced functionality, enabling code reuse and abstraction.

Q46. What is the difference between React Native and Flutter?

Intermediate
React Native uses JavaScript and bridges to native components, while Flutter uses Dart and its own rendering engine for UI, offering more consistent cross-platform UI.

Q47. What is lazy loading in React Native?

Intermediate
Lazy loading delays rendering of components or screens until they are needed, improving initial load time and performance.

Q48. What are React Native lifecycle methods?

Intermediate
Lifecycle methods include componentDidMount, componentDidUpdate, componentWillUnmount in class components, and useEffect in functional components.

Q49. What is the difference between UI thread and JS thread?

Intermediate
UI thread handles rendering and animations, while JS thread handles logic, events, and data processing. Heavy JS work can block UI if not optimized.

Q50. What is the difference between useCallback and useMemo?

Intermediate
useCallback memoizes functions to avoid unnecessary re-creations, while useMemo memoizes values or computations to prevent redundant calculations.

Q51. What is React Native Reanimated?

Intermediate
Reanimated is a library for building smooth, complex animations in React Native using native-driven animation APIs.

Q52. What is the difference between onPress and onLongPress?

Intermediate
onPress triggers an action when a component is tapped, while onLongPress triggers after holding the component for a defined duration.

Q53. What is the difference between React Native’s bridge and direct rendering?

Intermediate
The bridge allows JS to communicate with native modules asynchronously, while direct rendering reduces bridge overhead for better performance.

Q54. What is the difference between Inline styles and StyleSheet?

Intermediate
Inline styles are defined directly in JSX, while StyleSheet.create improves performance by creating immutable and optimized style objects.

Q55. What is error handling in React Native?

Intermediate
Error handling involves try/catch blocks, componentDidCatch, Error Boundaries, and using libraries to log and track runtime errors.

Q56. What is the difference between ScrollView and VirtualizedList?

Intermediate
ScrollView renders all content at once, suitable for small lists, while VirtualizedList efficiently renders only visible items for large lists.

Q57. What are React Native animations?

Intermediate
Animations include implicit (Animated API), explicit (AnimationController), and gesture-based animations to enhance UI interactions.

Q58. What is the difference between synchronous and asynchronous storage in React Native?

Intermediate
Synchronous storage blocks execution and can cause UI jank, while asynchronous storage like AsyncStorage allows non-blocking data access.

Q59. What are common debugging techniques in React Native?

Intermediate
Techniques include console.log, React DevTools, Flipper, breakpoints, Redux devtools, and using error boundaries to catch runtime errors.

Q60. What is React Native testing strategy?

Intermediate
Testing includes unit testing with Jest, integration testing, component testing with React Test Renderer, and end-to-end testing with Detox or Appium.

Q61. What are advanced state management techniques in React Native?

Experienced
Advanced techniques include Redux with middleware, MobX, Context API with useReducer, and Recoil for scalable and maintainable state management.

Q62. What is the difference between Redux Thunk and Redux Saga?

Experienced
Redux Thunk allows async actions using functions, while Redux Saga uses generator functions for more complex side effects and better action management.

Q63. What is the difference between native modules and JS modules?

Experienced
Native modules provide platform-specific functionality directly to JS via the bridge, whereas JS modules are pure JavaScript code running in the JS thread.

Q64. What are performance optimization techniques for large React Native apps?

Experienced
Techniques include using FlatList with keyExtractor, memoization, PureComponent, lazy loading, avoiding unnecessary re-renders, and optimizing images.

Q65. What is React Native’s bridge and how does it affect performance?

Experienced
The bridge enables asynchronous communication between JS and native threads. Excessive communication can cause performance issues and UI jank.

Q66. What are React Native Reanimated 2 benefits?

Experienced
Reanimated 2 runs animations on the UI thread, reducing bridge overhead, providing smoother animations, and enabling complex gesture-based interactions.

Q67. What is the difference between useEffect, useLayoutEffect, and componentDidMount?

Experienced
useEffect runs after render asynchronously, useLayoutEffect runs synchronously after DOM mutations, and componentDidMount is used in class components post-mount.

Q68. What is deep linking in React Native?

Experienced
Deep linking allows apps to handle URLs, directing users to specific screens within the app, useful for navigation, marketing, and sharing content.

Q69. What is the difference between controlled and uncontrolled inputs in large forms?

Experienced
Controlled inputs sync with state for validation and dynamic updates, while uncontrolled inputs manage their own internal state, suitable for simple forms.

Q70. What is the difference between Hermes and JSC in React Native?

Experienced
Hermes is a JavaScript engine optimized for React Native, improving startup time and memory usage, while JSC is the default JavaScript engine with standard performance.

Q71. What are advanced navigation techniques in React Native?

Experienced
Advanced navigation uses nested navigators, deep linking, dynamic routing with Navigator 2.0, and state preservation for complex navigation flows.

Q72. What are React Native animations strategies?

Experienced
Strategies include Animated API, Reanimated library, LayoutAnimation, and gesture-driven animations for smoother UI and high performance.

Q73. What is the difference between inline functions and useCallback?

Experienced
Inline functions recreate on each render causing re-renders, while useCallback memoizes functions to prevent unnecessary re-renders.

Q74. What is code splitting and lazy loading in React Native?

Experienced
Code splitting loads only the necessary code for a screen, while lazy loading delays component or module rendering to improve initial load performance.

Q75. What is the difference between React Native CLI and Expo for production apps?

Experienced
CLI offers full native control for production-ready customizations, while Expo simplifies development but may require ejecting for native code.

Q76. What are React Native performance profiling tools?

Experienced
Tools include React DevTools, Flipper, performance monitors, and built-in JS profiler for analyzing memory, CPU usage, and UI thread performance.

Q77. What is the difference between synchronous and asynchronous JS execution in React Native?

Experienced
Synchronous code blocks the JS thread affecting UI, while asynchronous code with Promises, async/await, or callbacks prevents UI freezing.

Q78. What is the difference between UI thread and JS thread in React Native?

Experienced
UI thread handles rendering and animations, while JS thread runs logic, events, and computations. Heavy JS work can block UI.

Q79. What are React Native testing strategies for large apps?

Experienced
Strategies include unit tests with Jest, component testing, snapshot testing, integration tests, and end-to-end testing with Detox or Appium.

Q80. What is server-side rendering (SSR) in React Native?

Experienced
React Native does not support SSR natively, but SSR concepts help pre-render data or content for hybrid web apps using React Native Web.

Q81. What is advanced error handling in React Native?

Experienced
Techniques include error boundaries, try/catch blocks, global error handlers, logging errors to services like Sentry, and graceful recovery.

Q82. What is the difference between VirtualizedList and FlatList?

Experienced
VirtualizedList is a base component for lists with large data, while FlatList is a specialized implementation optimized for common use cases.

Q83. What are best practices for memory management in React Native?

Experienced
Best practices include unmounting unused components, cleaning up listeners, optimizing images, and using PureComponent or memo to reduce memory usage.

Q84. What is the difference between Redux and Context API for large apps?

Experienced
Redux is better for predictable global state with middleware support, while Context API is suitable for simple state sharing without middleware overhead.

Q85. What is the difference between Animated API and Reanimated?

Experienced
Animated API runs animations on the JS thread, while Reanimated runs on the UI thread for smoother performance and complex animations.

Q86. What are best practices for handling navigation state in React Native?

Experienced
Use Navigator 2.0, maintain state in Redux or Context, preserve route state, handle deep linking, and avoid unnecessary re-renders.

Q87. What is the difference between NativeBase and React Native Paper?

Experienced
NativeBase provides pre-built UI components with customizable themes, while React Native Paper follows Material Design guidelines for consistent UI.

Q88. What is the difference between synchronous and asynchronous storage in React Native?

Experienced
Synchronous storage blocks JS execution and can cause UI jank, while AsyncStorage or MMKV allows non-blocking, asynchronous data access.

Q89. What are advanced debugging tools in React Native?

Experienced
Advanced tools include Flipper, React DevTools, Redux DevTools, Hermes profiler, performance monitor, and logging libraries for error tracking.

About React Native

React Native Interview Questions and Answers

React Native has revolutionized mobile app development by allowing developers to build cross-platform applications for both iOS and Android using a single codebase written in JavaScript. Companies worldwide prefer React Native for its efficiency, performance, and cost-effectiveness. As a React Native developer, mastering both fundamental and advanced concepts is essential to succeed in interviews and real-world projects.

At KnowAdvance.com, we provide a comprehensive set of React Native interview questions and answers curated for freshers and experienced developers. This guide covers React Native fundamentals, architecture, components, navigation, state management, performance optimization, and integration with native modules — everything you need to prepare for your next interview.

What is React Native?

React Native is an open-source framework developed by Facebook that enables building mobile applications using JavaScript and React. Unlike traditional native development, React Native allows developers to write a single codebase that runs on both iOS and Android platforms, using native components for optimal performance.

Core Features of React Native

  • Cross-Platform Development: Write once, deploy on both iOS and Android.
  • Reusable Components: Use pre-built or custom components to build UI efficiently.
  • Hot Reloading: Instantly view code changes without rebuilding the app.
  • Native Modules: Integrate platform-specific functionalities when needed.
  • Community Support: A large community providing libraries, tools, and frameworks.

React Native Architecture

Understanding the architecture of React Native is crucial for interviews. The key components include:

  • JavaScript Layer: Contains your React components and business logic.
  • Native Layer: Includes platform-specific UI components written in Swift, Objective-C, or Java/Kotlin.
  • Bridge: Facilitates communication between the JavaScript and Native layers, enabling asynchronous message passing.

Important React Native Concepts

To excel in interviews, you must be familiar with core React Native concepts:

  • Components: The building blocks of React Native UI, categorized into Functional and Class components.
  • Props: Short for “properties,” used to pass data from parent to child components.
  • State: Manages dynamic data inside components.
  • Hooks: Introduced in React 16.8 to manage state and lifecycle in functional components (e.g., useState, useEffect).
  • Navigation: Manage transitions between screens using React Navigation or React Native Navigation.
  • StyleSheet: For styling components using JavaScript objects similar to CSS.

Common React Native Interview Topics

Most React Native interviews focus on practical understanding and problem-solving abilities. Key areas include:

  • Understanding of React and React Native fundamentals.
  • Component lifecycle and hooks.
  • State management using Context API or Redux.
  • Navigation and routing between screens.
  • Integrating native modules and APIs.
  • Performance optimization and debugging techniques.
  • Testing frameworks like Jest and Detox.

State Management in React Native

Efficient state management is a critical aspect of React Native development. Interviewers often focus on your ability to handle global and local state:

  • Local State: Managed inside individual components using useState or this.state in class components.
  • Global State: Managed using Context API, Redux, or MobX.
  • Understand the differences between synchronous and asynchronous updates.

Navigation in React Native

Navigation is another crucial interview topic. React Native provides several libraries for managing screens:

  • React Navigation: Popular library for stack, tab, and drawer navigation.
  • React Native Navigation: Offers native navigation experience for complex apps.
  • Deep Linking: Handling URLs to navigate to specific screens in the app.

Networking and API Integration

Modern mobile apps require integration with REST or GraphQL APIs. Common practices include:

  • Using fetch API or Axios for HTTP requests.
  • Handling JSON responses and error handling.
  • Optimizing network calls using caching or pagination.

Performance Optimization

Interviewers often evaluate your ability to write performant React Native apps:

  • Use FlatList or SectionList for rendering long lists efficiently.
  • Avoid unnecessary re-renders using React.memo or useCallback hooks.
  • Minimize bridge communication between JavaScript and Native layers.
  • Optimize images using proper formats and lazy loading techniques.

Testing and Debugging

Testing ensures app stability and maintainability. Key tools include:

  • Jest: For unit testing React components and functions.
  • Detox: For end-to-end testing of mobile applications.
  • Reactotron: Debugging and inspecting React Native apps in real-time.

Popular React Native Interview Questions

  • What is React Native and how does it differ from React?
  • Explain the role of the Bridge in React Native.
  • What are the differences between functional and class components?
  • How do you manage state in large-scale React Native apps?
  • What is the difference between React Navigation and React Native Navigation?
  • How do you optimize performance in React Native applications?
  • Explain how hooks like useEffect and useMemo work.
  • What are native modules and when would you use them?
  • How do you handle asynchronous API calls in React Native?
  • What testing frameworks are commonly used for React Native?

In the next part, we will cover advanced React Native topics such as native module integration, animations, app security, deployment to App Store and Play Store, performance tuning, and practical interview strategies to fully prepare you for technical interviews.

Advanced React Native Interview Preparation

After mastering the fundamentals of React Native, interviews often focus on advanced topics that demonstrate your ability to build robust, efficient, and production-ready mobile applications. These topics include native module integration, animations, app security, performance optimization, and deployment strategies.

Integration with Native Modules

React Native allows you to access native platform capabilities when necessary. Understanding native modules is crucial for complex applications.

  • Android Modules: Written in Java or Kotlin to access Android-specific APIs.
  • iOS Modules: Written in Objective-C or Swift to integrate with iOS functionalities.
  • Bridge communication allows JavaScript code to call native methods asynchronously.

Interview questions may include:

  • What is a native module in React Native and when should you use it?
  • How does the JavaScript-to-Native bridge work?
  • Explain a scenario where you integrated a custom native module.

Animations and UI Enhancements

React Native provides powerful tools for creating smooth and interactive user interfaces:

  • Animated API: For declarative animations of components.
  • Reanimated 2: A high-performance animation library that allows running animations on the UI thread.
  • Lottie: Integrate JSON-based animations for engaging UI experiences.

State Management at Scale

For large applications, effective state management is critical. Interviewers often focus on Redux, Context API, or MobX:

  • Redux: Centralizes state management using actions, reducers, and store.
  • Context API: Lightweight solution for simple global state management.
  • MobX: Reactive state management library that automatically tracks state changes.

Performance Optimization

High-performance apps provide better user experiences and are highly valued in technical interviews:

  • Minimize unnecessary re-renders using React.memo and useCallback.
  • Use FlatList and SectionList for large datasets to optimize memory usage.
  • Optimize images using proper formats, compression, and lazy loading.
  • Move heavy computations off the main thread using InteractionManager or background tasks.

App Security Best Practices

Security is a key consideration in mobile app development:

  • Secure sensitive data using Keychain on iOS and EncryptedSharedPreferences on Android.
  • Use HTTPS and SSL pinning for all API communications.
  • Minify and obfuscate JavaScript code using Metro bundler or third-party tools.
  • Handle authentication and authorization securely using JWT tokens or OAuth 2.0.

Testing React Native Apps

Testing ensures app reliability and maintainability. Key tools include:

  • Jest: Unit testing of components and functions.
  • React Native Testing Library: For testing component rendering and interactions.
  • Detox: End-to-end testing framework for mobile apps.
  • Continuous integration with CI/CD pipelines ensures that tests are run automatically on every code change.

Deployment to App Stores

Deploying React Native apps requires knowledge of both Google Play Store and Apple App Store:

  • Configure platform-specific build files (Android: Gradle, iOS: Xcode).
  • Sign apps with release keys and provisioning profiles.
  • Use Fastlane for automating build and deployment processes.
  • Test beta releases using Google Play Beta testing and TestFlight.

Common React Native Interview Questions (Advanced)

  • How do you optimize React Native app performance for large lists?
  • Explain the use of Redux middleware and why it’s important.
  • How do you integrate a native module for platform-specific functionality?
  • What are best practices for handling animations in React Native?
  • How do you secure sensitive user data in a React Native app?
  • Describe the differences between React.memo, useMemo, and useCallback.
  • How do you implement deep linking in a React Native app?
  • Explain the steps for deploying React Native apps to Play Store and App Store.

Best Practices for React Native Interviews

To excel in React Native interviews, consider the following tips:

  • Build a portfolio of real-world apps demonstrating navigation, state management, API integration, and animations.
  • Understand both React and React Native fundamentals thoroughly.
  • Practice coding problems in JavaScript and React Native environment.
  • Stay updated with the latest React Native releases and community libraries.
  • Be prepared to explain your architectural and design choices in apps you’ve built.

Career Opportunities with React Native Skills

Proficiency in React Native opens opportunities in startups, enterprise projects, and cross-platform development roles. Positions include:

  • React Native Developer
  • Mobile Application Engineer
  • Full-Stack Developer with mobile expertise
  • UI/UX Engineer for mobile platforms

Conclusion

React Native is an increasingly popular framework for building cross-platform mobile applications. By mastering both fundamental and advanced topics — including components, hooks, state management, navigation, performance optimization, security, testing, and deployment — you can confidently excel in interviews and create professional, high-quality mobile applications. The comprehensive React Native interview questions and answers on KnowAdvance.com will help you prepare effectively and succeed in your career as a React Native developer.