React Native interview questons

1. What is React Native?

Answer: React Native is an open-source mobile application framework created by Facebook, Inc. It allows developers to use React along with native platform capabilities to build mobile apps for iOS and Android using JavaScript and React.

2. How does React Native differ from React?

Answer: React Native is a framework for building native mobile apps using React. While React is a JavaScript library for building user interfaces, primarily for web applications, React Native uses native components instead of web components as building blocks.

3. What are the main components of a React Native application?

Answer: The main components include:

• **View**: A container that supports layout with flexbox, style, touch handling, and accessibility controls.

• **Text**: A component for displaying text.

• **Image**: A component for displaying images.

• **ScrollView**: A generic scrolling container that can host multiple components and views.

• **StyleSheet**: Provides an abstraction similar to CSS stylesheets.

4. Explain the use of the Flexbox layout model in React Native.

Answer: Flexbox is a layout model that allows responsive layout to be built more easily. It enables a flexible and efficient arrangement of components within a container, even when their size is unknown or dynamic. React Native uses Flexbox for layout, which works the same way as it does in CSS on the web but with some differences.

5. What is a bridge in React Native?

Answer: The bridge in React Native is a bidirectional communication channel between JavaScript and the native environment. It allows JavaScript code to call native functions and vice versa, enabling the use of native capabilities.

6. How do you handle state management in React Native?

Answer: State management in React Native can be handled using local component state, Context API for simple applications, or external libraries like Redux, MobX, or React Query for more complex applications.

7. What are props in React Native?

Answer: Props (short for properties) are read-only components that must be passed to the component as an input. They allow parent components to pass data to child components.

8. How do you navigate between screens in a React Native app?

Answer: Navigation in React Native can be implemented using libraries such as React Navigation or React Native Navigation, which provide a variety of navigators, such as stack, tab, and drawer navigators.

9. What is the purpose of the `FlatList` component?

Answer: `FlatList` is a component used to render lists of data efficiently. It is highly performant and scalable to large lists of data. It supports features like lazy loading, pull to refresh, and infinite scrolling.

10. How can you improve the performance of a React Native application?

Answer: Performance can be improved by optimizing images, using `shouldComponentUpdate` or React.memo, minimizing the use of state and props, avoiding unnecessary re-renders, and using native modules for heavy operations.

11. What are native modules in React Native?

Answer: Native modules are code libraries written in native languages (Java/Kotlin for Android, Objective-C/Swift for iOS) that can be invoked from JavaScript, allowing React Native apps to access platform-specific functionalities.

12. Explain the lifecycle of a React Native component.

Answer: The lifecycle of a React Native component includes mounting (constructor, static getDerivedStateFromProps, render, componentDidMount), updating (static getDerivedStateFromProps, shouldComponentUpdate, render, getSnapshotBeforeUpdate, componentDidUpdate), and unmounting (componentWillUnmount) phases.

13. How does React Native handle styling?

Answer: React Native uses JavaScript objects for styling, similar to CSS but with a camelCase syntax. Styles are applied using the `StyleSheet.create` method, which validates the styles and improves performance.

14. What is Expo?

Answer: Expo is an open-source platform for making universal native apps with React Native. It provides a set of tools and services that simplify the development, build, deployment, and iteration process for React Native apps.

15. How do you test React Native applications?

Answer: React Native applications can be tested using Jest for unit testing, Detox or Appium for end-to-end testing, and React Native Testing Library for component testing.

16. Explain hot reloading and live reloading in React Native.

Answer: Hot reloading applies changes to the source code in real-time without reloading the entire app, maintaining the app state. Live reloading reloads the entire app upon file changes, losing the current state.

17. What is the Virtual DOM?

Answer: The Virtual DOM is a concept where a virtual representation

of the UI is kept in memory, which React uses to optimize updates to the real DOM for performance improvements.

18. Describe how you can make HTTP requests in React Native.

Answer: HTTP requests in React Native can be made using the Fetch API or third-party libraries like Axios for making network requests to REST APIs.

19. What are hooks in React Native?

Answer: Hooks are functions that let you use state and other React features in functional components. They include useState, useEffect, useContext, and others.

20. How do you secure sensitive information in a React Native app?

Answer: Sensitive information can be secured using secure storage solutions like React Native Keychain or SecureStore from Expo, which encrypt data and store it securely on the device.

21. What are the limitations of React Native?

Answer: Limitations include performance issues for complex animations and interactions, longer initial load times, and the need for native code for certain functionalities not supported by React Native or third-party libraries.

22. How do you handle image caching in React Native?

Answer: Image caching can be handled using libraries like react-native-fast-image, which provides advanced image caching capabilities and performance improvements over the default Image component.

23. What is CodePush?

Answer: CodePush is a cloud service that enables React Native developers to deploy mobile app updates directly to users’ devices, allowing quick fixes and updates without going through the app store approval process.

24. Explain how to use custom fonts in React Native.

Answer: Custom fonts can be added by including the font files in the project and linking them using React Native Link or manually in the native iOS and Android project settings, and then specifying the font family in the style.

25. How does React Native handle device orientation changes?

Answer: Device orientation changes can be handled using the Dimensions API to get screen dimensions and applying conditional styling or using libraries like react-native-orientation to lock or respond to orientation changes.

26. What is React Native CLI?

Answer: React Native CLI (Command Line Interface) is a toolchain for initializing, developing, and debugging React Native apps. It provides commands for creating new projects, running them on simulators and devices, and preparing them for production.

27. How do you implement animations in React Native?

Answer: Animations can be implemented using the Animated API for basic animations, the LayoutAnimation API for automatic animations upon layout changes, or third-party libraries like react-native-reanimated for more complex animations.

28. What is Hermes?

Answer: Hermes is an open-source JavaScript engine optimized for running React Native on Android. It improves app performance and startup times.

29. How do you integrate a React Native app with a backend service?

Answer: Integration can be done using HTTP requests with Fetch or Axios to interact with REST APIs, or using libraries like Apollo Client for GraphQL APIs. Authentication and data exchange are typically handled via tokens.

30. How can you debug a React Native application?

Answer: Debugging can be done using the built-in debugger, React Native Debugger, Chrome DevTools, or third-party services like Flipper or Reactotron for more advanced debugging capabilities.

Fell free to checkout latest React Native jobs in kerala