React Native Interview Questions and Answers for 2025 – Beginner to Advanced | JaganInfo

React Native is a JavaScript framework for building native mobile apps using React principles, targeting both Android and iOS platforms.

React is for building web interfaces using the virtual DOM, whereas React Native builds native mobile UI components instead of HTML.

Core components include View, Text, Image, ScrollView, TextInput, and Button, analogous to HTML elements but native.

JSX is a syntax extension that lets you write markup-like code in JavaScript to define UI components.

Styling is done using a StyleSheet object with CSS-like styles but camelCase properties.

Flexbox is the layout system used in React Native to arrange components in rows or columns flexibly.

Props are immutable inputs from parent components; state holds mutable data internal to the component affecting rendering.

Lifecycle includes mounting, updating, and unmounting phases. Functional components use hooks like useEffect for side effects.

Hot Reloading updates UI instantly on code changes without losing the app state, aiding developer productivity.

Yes, via APIs and native modules for camera, GPS, accelerometer, contacts, etc.

React Native uses a Virtual DOM abstraction to batch and optimize updates sent via a bridge to native UI components.

Controlled components have value managed via React state; uncontrolled rely on native DOM for state management.

Hooks are functions enabling state and lifecycle management in functional components, e.g., useState, useEffect, useContext.

Libraries like React Navigation provide stack, tab, and drawer navigators for routing and screen transitions.

Class components use ES6 classes and lifecycle methods; functional components use hooks for similar functionality.

Use PureComponent, React.memo, optimize FlatList, avoid unnecessary renders, lazy load components.

Bridge enables asynchronous communication between JavaScript and native code modules for accessing native functionality.

Use Flexbox, Dimensions API, PixelRatio, and percentage-based styling for responsive layouts.

React Native uses native APIs and libraries like react-native-permissions to request and manage runtime permissions.

Live Reload reloads entire app losing state; Hot Reload updates only changed modules preserving state.

Redux is a predictable state container used to manage global state across components efficiently.

Middleware intercepts actions for async tasks, logging, or conditional dispatch; popular ones are Redux Thunk and Saga.

Use React Native Debugger, Flipper, Chrome DevTools, or VS Code debugger with breakpoints and profiling tools.

Native modules allow writing native platform code (Objective-C, Java) for functionality unavailable in JavaScript.

Use lazy loading, minimize bundle size, enable Hermes engine, defer heavy processing on startup.

Hermes is a lightweight JS engine optimized to enhance React Native app startup, memory use, and performance.

Use local databases (Realm, SQLite) and background sync with queued changes on connectivity restoration.

Unit testing with Jest, component testing with Enzyme or React Test Renderer, and end-to-end testing with Detox or Appium.

Use libraries like react-native-i18n or i18next to support multiple languages and locale formats.

Avoid storing sensitive data in JS, use encrypted storage, enable SSL pinning, validate inputs, and keep dependencies updated.

Redux follows a unidirectional data flow with a single immutable store, actions, and reducers managing state changes predictably.

Used for async flows, logging, crash reporting, routing, handling side effects in Redux ecosystems.

Use source maps, React DevTools, Flipper plugins, Hermes profiler, and console logs effectively.

Write platform-specific code in Java/Objective-C, expose APIs via React Native bridge, and handle callbacks/events.

Includes JavaScript thread, native thread, and the bridge facilitating communication between them asynchronously.

The process whereby React compares new and old virtual DOM trees and determines the minimal DOM operations required to update the UI.

Use React DevTools Profiler, profiling in Flipper, and Hermes Profiler to diagnose performance bottlenecks.

Use HTTPS, token-based authentication, certificate pinning, and secure storage for credentials and tokens.

Configure URL schemes and intent filters; use deep linking libraries to route app navigation from external links.

Code Push is a cloud service that enables pushing JavaScript code updates directly to devices without app store release.

Expo offers an easy-to-use platform with managed workflow but limits native code customization; React Native CLI offers full access but requires more setup.

Use Gesture Responder System or libraries like react-native-gesture-handler for handling touch gestures with good performance.

LayoutAnimation API enables smooth, native-driven animations of layout changes.

Bridge facilitates cross-language communication but is asynchronous and can cause performance overhead if overused.

Inline styles are objects defined directly in components; external styles use StyleSheet.create for better performance and reusability.

Relies on JS garbage collection and native platform memory management, optimized for minimal leaks and efficient usage.

Challenges include performance bottlenecks, platform-specific bugs, native module bridging, and managing third-party dependencies.

Use Flipper plugins, native debugger integration, logging enhancements, remote debugging, and profiling tools.

Batch requests, use caching strategies, debounce inputs, and minimize bridge calls for network efficiency.

Component-based architecture, modular code, lazy loading, memoization, and effective state management improve scalability.