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Infosys · React Native
Practice React Native questions specifically asked in Infosys interviews – ideal for online test preparation, technical rounds and final HR discussions.
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26
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Infosys
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React Native
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Go through each question and its explanation. Use this page for targeted revision just before your Infosys React Native round.
Props are read-only inputs passed to a component from its parent. For example, a button can receive a label as a prop. State is data managed within the component and can change dynamically, like a counter. Changing state triggers a re-render, while props update when parents re-render.
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React Native does not support traditional CSS files because it doesn’t use a web DOM. Styling is done using JavaScript objects, StyleSheet.create, or third-party libraries like styled-components. Each style is written using camelCase property names similar to CSS but interpreted natively by the platform.
Use flex when you want elements to automatically fill available space relative to siblings. Fixed or percentage widths are suitable for predictable layouts, while flex is better for dynamic screens that vary in size or orientation.
React Navigation is a popular library for managing navigation in React Native apps. It allows developers to move between screens, handle stacks, tabs, and drawers, and maintain a predictable navigation state across the app.
You can pass parameters to another screen by adding an object as the second argument to navigation.navigate. The receiving screen accesses the data via route.params.
navigation.navigate('Details', { id: 10 });The navigation stack works on the principle of push and pop. When a screen is opened using navigation.navigate, it’s pushed on top of the stack. When you press the back button or call navigation.goBack(), the current screen is popped off and control returns to the previous one.
Redux provides a single centralized store that holds all application state. It ensures consistent behavior and makes debugging easier with tools like Redux DevTools.
The Context API is simple and built into React. It works well for small-scale global data like themes or user preferences. Redux, on the other hand, provides structured state management with reducers, middleware, and debugging tools, making it better for large, complex apps with frequent updates.
The Fetch API is a built-in JavaScript method for making network requests. It returns a promise and allows handling of JSON data easily using async / await or then / catch.
fetch('https://api.example.com/data').then(res => res.json());You can use libraries like react-query or AsyncStorage to cache responses locally. Caching reduces network calls and improves performance by serving previously fetched data instantly.
Native modules allow React Native apps to access native platform features like camera, sensors, or Bluetooth using Java or Swift. They bridge the gap between JavaScript and native environments so both can communicate seamlessly.
The React Native bridge serializes function calls and arguments into JSON messages. These messages travel asynchronously between JavaScript and native threads for two-way communication.
JSI allows JavaScript to call native code directly without using asynchronous JSON serialization. It improves performance by removing the overhead of message passing, enabling synchronous function calls and direct memory sharing between JS and native code.
FlatList uses lazy loading and virtualization, meaning only items currently visible on the screen are rendered. This drastically reduces memory usage and improves performance on large lists.
Forgetting to clear intervals, event listeners, or subscriptions in useEffect cleanup functions can lead to memory leaks. These leaks cause the app to retain unnecessary memory, affecting performance over time.
Jest is a testing framework developed by Meta for unit and snapshot testing in JavaScript and React Native apps. It provides built-in mocking, code coverage, and a zero-config setup for fast feedback.
test('renders correctly', () => { const tree = renderer.create(<App />).toJSON(); expect(tree).toMatchSnapshot(); });GitHub Actions provides a YAML-based CI/CD workflow directly inside the repository. You can automate testing, building, and deployment for React Native apps across Android and iOS targets.
CI/CD ensures continuous integration of code changes and automated delivery to testers or app stores. It improves team collaboration, reduces manual errors, and speeds up release cycles through automation and consistent build validation.
TurboModules use JSI to directly call native functions synchronously. This makes data exchange between JS and native modules faster and more memory-efficient compared to the old bridge system.
Yes, React Native supports gradual migration. Both the old bridge and new architecture can coexist during transition. This hybrid mode helps teams adopt JSI, TurboModules, and Fabric without breaking existing modules.
React Native has class components that use ES6 classes and functional components that are simple functions returning JSX. Functional components are preferred in modern React Native because they work seamlessly with hooks.
Unoptimized or large images consume significant memory and slow down UI rendering. Use the Image component’s caching features, serve WebP formats, and load lower-resolution thumbnails for previews to enhance speed.
When two components need to share the same data, it’s best to lift the state up to their common ancestor and pass it down through props. This pattern keeps data consistent and avoids duplication.
React is a library for building web interfaces using HTML elements like <div> and <p>. React Native replaces these with mobile-native components such as <View> and <Text>, allowing JavaScript to render actual native UI components.
The useState hook lets you add internal component state to functional components. It returns a pair: the current state value and a function to update it.
const [count, setCount] = useState(0);
Class components use ES6 classes and can access lifecycle methods like componentDidMount. Functional components are plain functions that return JSX and rely on hooks (like useState and useEffect) to manage state and side-effects. Functional components are now the standard approach—they are shorter, easier to test, and better optimized by React.