React-Native Interview Questions & Answers

1. What is React Native?

   • Answer: React Native is an open-source framework developed by Facebook that allows you to build mobile applications using JavaScript and React.

2. Explain the key differences between React and React Native.

   • Answer: React is a JavaScript library for building user interfaces on the web, while React Native is a framework for building mobile applications using React and native components.

3. How does React Native work?

   • Answer: React Native uses JavaScript to interact with native components through a bridge. The JavaScript code runs in a background thread and communicates with the native modules.

4. What is JSX?

   • Answer: JSX is a syntax extension for JavaScript recommended by React. It looks similar to XML/HTML and gets transpiled to JavaScript.

5. Explain the virtual DOM and its significance in React Native.

   • Answer: The virtual DOM is an in-memory representation of the real DOM elements. React uses it to efficiently update the actual DOM when the state of a component changes, improving performance.

6. What are props in React Native?

   • Answer: Props (short for properties) are used to pass data from a parent component to a child component in React Native.

7. Describe the state in React Native.

   • Answer: The state is an object that represents the parts of the app that can change over time. It is used to create dynamic and interactive components.

8. What is the purpose of setState()?

   • Answer: setState() is a method used to update the state of a React Native component. It triggers a re-render of the component with the updated state.

9. What are React Native Hooks?

   • Answer: Hooks are functions that allow you to use state and lifecycle features in functional components instead of class components.

10. Explain the significance of useEffect() hook.

    • Answer: useEffect() is a hook used for side effects in functional components, such as data fetching, subscriptions, or manually changing the DOM.

11. What is the purpose of AsyncStorage in React Native?

    • Answer: AsyncStorage is a simple, unencrypted, asynchronous storage system in React Native used for storing key-value pairs locally.

12. Describe the purpose of React Native Navigation.

    • Answer: React Native Navigation is a library for handling navigation in React Native applications. It provides tools to navigate between screens and manage the navigation stack.

13. What is Redux, and how does it work with React Native?

    • Answer: Redux is a state management library. In React Native, it helps manage the global state of the application, making it easier to pass data between components.

14. Explain the concept of Higher Order Components (HOCs).

    • Answer: HOCs are functions that take a component and return a new component with additional props, enabling code reuse and logic abstraction.

15. What is the significance of the Flexbox layout in React Native?

    • Answer: Flexbox is a layout model that allows you to design complex layouts in a more efficient and predictable way, especially for mobile applications.

16. Describe the purpose of the FlatList component in React Native.

    • Answer: FlatList is a component used to efficiently render a large list of items by only rendering the items that are currently visible on the screen.

17. What is the significance of the TouchableOpacity component?

    • Answer: TouchableOpacity is a touchable wrapper component that provides visual feedback for touchable elements, making them appear as if they are pressed.

18. Explain the concept of React Native Bridge.

    • Answer: The React Native Bridge is a communication layer that allows JavaScript code to interact with native modules in order to access device-specific functionality.

19. How do you debug a React Native application?

    • Answer: React Native provides tools like React DevTools and the built-in debugger to inspect and debug applications. Additionally, console.log statements are commonly used.

20. What are the advantages of using Expo with React Native?

    • Answer: Expo is a set of tools and services that simplifies React Native development, providing features like a development server, easy configuration, and access to native modules without the need for manual linking.

21. Explain the purpose of the StyleSheet in React Native.

    • Answer: StyleSheet is a utility in React Native used to define styles in a more efficient way, with optimization for runtime performance.

22. How can you handle user input in React Native?

    • Answer: User input can be handled using components like TextInput for text input, Touchable components for button presses, and event handlers like onChangeText and onPress.

23. Describe the purpose of the Navigator in React Navigation.

    • Answer: The Navigator in React Navigation is used for managing the navigation stack and rendering screens in a React Native application.

24. What are React Native components and props?

    • Answer: Components are the building blocks of a React Native application, while props are used to pass data from one component to another.

25. How do you handle network requests in React Native?

    • Answer: Network requests can be handled using the fetch API, third-party libraries like Axios, or built-in solutions like XMLHttpRequest.

26. What is the purpose of the key prop in React Native?

    • Answer: The key prop is used to uniquely identify and distinguish between different elements in a list, aiding React Native in efficient updates and re-rendering.

27. Explain the concept of state lifting in React Native.

    • Answer: State lifting involves moving the state from a child component to a parent component to share the state among multiple components.

28. How do you handle images in React Native?

    • Answer: Images can be handled using the Image component in React Native, with support for local and network images.

29. What is the purpose of the cloneElement method in React Native?

    • Answer: cloneElement is a method that creates a new React element with the same type and props as another element, allowing you to modify or add new props.

30. Explain the concept of the Context API in React Native.

    • Answer: The Context API allows you to share values like themes or authentication status between components without explicitly passing them through props.

31. How can you optimize the performance of a React Native application?

    • Answer: Performance optimization can be achieved by using PureComponent, memoization, optimizing renders, and employing tools like React DevTools.

32. Describe the purpose of the shouldComponentUpdate method.

    • Answer: shouldComponentUpdate is a lifecycle method that determines whether a component should re-render, optimizing performance by preventing unnecessary renders.

33. What is the significance of the TouchableWithoutFeedback component?

    • Answer: TouchableWithoutFeedback is a touchable wrapper component that doesn't provide any visual feedback when pressed, making it suitable for custom touch handling.

34. **How do you implement animations

in React Native?** - Answer: React Native supports animations through the Animated API, which allows you to create smooth and performant animations.

35. Explain the purpose of the React.memo function.

    • Answer: React.memo is a higher-order component that memoizes the rendered output of a functional component, preventing unnecessary renders.

36. What is the purpose of the onLayout event in React Native?

    • Answer: The onLayout event is triggered when the layout of a component changes, providing information about the updated dimensions.

37. How do you handle navigation between screens in React Native?

    • Answer: Navigation between screens can be managed using libraries like React Navigation, which provides navigators such as StackNavigator and TabNavigator.

38. Explain the purpose of the SafeAreaView component.

    • Answer: SafeAreaView is a component that ensures that its children are not obscured by the device's status bar, notched areas, or home indicator.

39. What is the purpose of the useReducer hook in React Native?

    • Answer: useReducer is a hook that allows you to manage state in a more complex and predictable way, especially when the state logic becomes intricate.

40. Describe the purpose of the WebView component in React Native.

    • Answer: WebView is a component that allows you to embed web content within a React Native application.

41. How do you handle forms in React Native?

    • Answer: Forms can be handled by using the TextInput component for input fields, handling state changes, and implementing form submission logic.

42. Explain the concept of debouncing and throttling in React Native.

    • Answer: Debouncing and throttling are techniques used to control the frequency of a function call, especially useful for handling user input and preventing unnecessary calls.

43. What is the purpose of the ActivityIndicator component?

    • Answer: ActivityIndicator is a component that displays a loading indicator, signaling to the user that some background process is in progress.

44. How can you handle deep linking in React Native?

    • Answer: Deep linking can be handled using libraries like React Navigation, which provides support for linking to specific screens within the app.

45. Explain the purpose of the AppState module in React Native.

    • Answer: The AppState module allows you to detect whether the app is in the foreground or background, enabling you to handle application state changes.

46. How do you handle device orientation changes in React Native?

    • Answer: Device orientation changes can be handled using the react-native-orientation library or by subscribing to the Dimensions change event.

47. What is the purpose of the Linking module in React Native?

    • Answer: The Linking module is used to open URLs, deep link into the app, or check if the app can open a given URL.

48. How can you integrate third-party libraries in a React Native project?

    • Answer: Third-party libraries can be integrated using package managers like npm or yarn, and linking can be done manually or using tools like react-native link.

49. Explain the purpose of the PixelRatio module in React Native.

    • Answer: PixelRatio is a module that provides methods for converting between device-independent pixels (dips) and pixels.

50. What are the benefits and drawbacks of using React Native for mobile app development?

    • Answer: Benefits include code reuse, fast development, and the ability to deploy on multiple platforms. Drawbacks may include performance limitations in highly complex applications and potential challenges with integrating certain native modules.