React native interview questions and answers

React Masters
6 min readApr 5, 2024

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React JS:

React.js, regularly referred to as React, is an open-source JavaScript library for building client interfacing, especially for single-page applications. Created and kept up by Facebook, React has picked up immense popularity in the web improvement community for its proficiency, simplicity, and flexibility.

One of React’s center standards is the concept of reusable components, which permit engineers to make secluded pieces of code that can be effectively composed together to construct complex client interfaces. These components typify both the structure and behavior of a UI component, making it less demanding to oversee and keep up large-scale applications.

React Native:

React Native, crafted by Facebook, stands as an open-source JavaScript framework tailored for native mobile app development. Rooted in the JavaScript library React, it streamlines the creation process of genuine native mobile applications.

This framework boasts a significant advantage in time efficiency, allowing developers to construct fully functional native mobile apps using a singular language: JavaScript. This means that with React Native, you code once and seamlessly across both Android and iOS platforms. The resulting React Native app inherits the distinctive native appearance and behavior, ensuring a polished user experience.

TOP 10 interview Questions & answers of React Native:

1. What is React Native?
React Native is an open-source framework developed by Facebook for building native mobile applications using JavaScript and React. It allows developers to create cross-platform apps that render using native components, providing a native-like user experience.

2. Explain the difference between React Native and React.
React is a JavaScript library for building user interfaces, primarily for web applications, while React Native is a framework for building native mobile applications. React uses virtual DOM to render UI components, whereas React Native compiles JavaScript code into native code for each platform.

3. What are the advantages of using React Native for mobile app development?
Cross-platform compatibility
Native performance
Reusable components
Hot reloading for faster development
Large ecosystem and community support
Cost-effectiveness

4. How does React Native achieve cross-platform compatibility?
React Native achieves cross-platform compatibility by using a single codebase written in JavaScript, which is then compiled into native code for each platform (Android and iOS). This allows developers to write once and deploy on multiple platforms.

5. What is the purpose of JSX in React Native?
JSX (JavaScript XML) is a syntax extension used in React Native (and React) to describe what the UI should look like. It allows developers to write HTML-like code within JavaScript, making it easier to write and understand UI components.

6. Explain the concept of props in React Native.
Props (short for properties) are a way to pass data from parent to child components in React Native. They are immutable and are used to customize and configure child components based on their parent’s requirements.

7. What are state and setState in React Native?
State is a JavaScript object that represents the current condition or data of a component. setState is a method provided by React Native to update the state of a component, triggering a re-render of the UI based on the updated state.

8. What is the purpose of AsyncStorage in React Native?
AsyncStorage is a built-in storage system in React Native used for storing and retrieving data persistently on the device. It is commonly used for storing user preferences, authentication tokens, and other application data.

9. How does React Native handle navigation between screens?
React Native provides various navigation libraries such as React Navigation and React Native Navigation for handling navigation between screens. These libraries allow developers to define navigation stacks, tabs, and drawers to navigate between different parts of the application.

10. Explain the concept of Redux in React Native and its benefits.
Redux is a state management library commonly used with React Native (and React) applications. It provides a centralized store to manage the state of the entire application, making it easier to maintain and debug complex state logic. Redux enables predictable state management and facilitates communication between components.

TOP 10 React Native advanced interview questions:

1. What are the differences between React Native and native development?
React Native allows developers to build cross-platform mobile applications using JavaScript and React, whereas native development involves building separate codebases for each platform (iOS and Android) using their respective languages (Swift/Obj-C for iOS, Java/Kotlin for Android).

2. Explain how React Native bridges work and why they are important.
React Native bridges are responsible for communicating between JavaScript code and native code. They enable React Native apps to access platform-specific APIs and components. Understanding bridges is crucial for integrating native functionality into React Native apps and optimizing performance.

3. Describe the architecture of a typical React Native application.
A typical React Native application consists of JavaScript code running on a JavaScript engine (e.g., JavaScriptCore) communicating with native modules through bridges. Native modules interact with platform-specific APIs and components to render UI elements and handle device features.

4. What are the key differences between React Navigation and React Native Navigation? When would you choose one over the other?
React Navigation is a JavaScript-based navigation library, while React Native Navigation is a native navigation library. React Navigation is often preferred for its simplicity and cross-platform support, while React Native Navigation offers better performance and native feel but requires more setup.

5. How would you optimize the performance of a React Native application?
Performance optimization in React Native involves techniques like minimizing the use of heavy computations in the main thread, using PureComponent and memoization for efficient rendering, lazy loading components, optimizing images, and utilizing tools like Hermes and Flipper for debugging and profiling.

6. Explain the role of FlatList and VirtualizedList in React Native, and when would you use each one?
FlatList and VirtualizedList are components in React Native used for rendering large lists efficiently. FlatList is suitable for simple lists with homogeneous data, while VirtualizedList provides more customization options and is suitable for complex lists with heterogeneous data and dynamic content.

7. How would you handle state management in a large-scale React Native application?
State management in large-scale React Native applications can be handled using libraries like Redux, MobX, or Context API. These libraries provide centralized stores to manage application state, facilitate data flow between components, and ensure predictable state management.

8. Explain the concept of native module development in React Native. Provide an example of when you would need to develop a custom native module.
Native module development involves writing platform-specific code (e.g., Java for Android, Objective-C/Swift for iOS) to expose native functionality to JavaScript in React Native applications. Custom native modules are needed when integrating platform-specific APIs (e.g., accessing device sensors, implementing custom UI components) not available in JavaScript.

9. What are the challenges of testing React Native applications, and how would you address them?
Challenges of testing React Native applications include setting up testing environments, mocking native modules, handling asynchronous code, and testing UI components across different platforms. These challenges can be addressed by using testing frameworks like Jest, Detox, and React Native Testing Library, along with proper mocking and snapshot testing techniques.

10. Discuss the differences between Hermes and JavaScriptCore in React Native, and when would you choose one over the other.
Hermes is a JavaScript engine optimized for React Native, offering better performance and reduced memory footprint compared to JavaScriptCore. Hermes is suitable for production apps targeting Android platforms, while JavaScriptCore is still used for iOS apps and development/debugging purposes.

Conclusion:

These advanced React Native interview questions gain into various aspects of React Native development, requiring a deep understanding of the framework’s architecture, performance optimization techniques, navigation libraries, state management solutions, and native module development.

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