React Native interview questions and answers

1. Raw text in React Native

In React Native, <View>Order placed</View> throws an error. Why?

1. A.View cannot have any children
2. B.Text strings must be inside a <Text> component
3. C.React Native needs <div> for text
4. D.Strings must be passed as a title prop

2. Starting a new React Native app

What do the React Native docs recommend for starting a new app in 2026?

1. A.Create React App with a mobile template
2. B.Writing Java and Swift first, then adding React
3. C.A framework such as Expo
4. D.Using a WebView that loads the website

3. Why list items need keys

Why should every item in a React Native FlatList have a stable, unique key?

1. A.Keys tell FlatList which images to cache in memory, so recycled rows scroll faster and do not reload their pictures
2. B.Keys are required before list items can receive touch events
3. C.Keys let React match items between renders, so it updates, reorders and keeps item state correctly
4. D.Keys are read out as accessibility labels by screen readers

4. Text outside a Text component

A React Native component returns `<View>Hello</View>`. What happens?

1. A.It renders Hello in the default system font and colour
2. B.It renders nothing at all and logs no warning
3. C.It throws: text strings must be rendered within a <Text> component
4. D.It works on Android but is ignored on iOS

5. Default flexDirection in React Native

Three Views are placed inside a parent View with no style. How are they laid out?

1. A.Stacked vertically, because flexDirection defaults to column
2. B.Side by side, because flexDirection defaults to row
3. C.On top of each other, because position defaults to absolute
4. D.In a wrapping grid, because flexWrap defaults to wrap

6. Why React Native uses Hermes

Hermes is the default JavaScript engine for React Native. What is its main benefit on phones?

1. A.Faster startup, as JS is precompiled to bytecode at build time
2. B.It runs the JavaScript on the GPU for faster drawing
3. C.It converts the JavaScript into Swift and Kotlin source
4. D.It removes the need for any native code inside the app

7. What EAS Build is for

What does Expo Application Services (EAS) Build provide?

1. A.A database for storing user profiles
2. B.Cloud builds of signed Android and iOS binaries
3. C.A testing framework for React components
4. D.A design tool for creating app icons

8. Detecting app moving to background

You want to pause a video when the user switches to another app. Which React Native API reports this?

1. A.AppState, with values like active and background
2. B.Dimensions, with a change event on resize
3. C.PixelRatio, with a background flag
4. D.Vibration, with a pause listener

9. End-to-end tests for a React Native app

Which tool runs end-to-end tests that tap through a real React Native app on a simulator or device?

1. A.Detox or Maestro
2. B.ESLint or Prettier
3. C.Metro or Babel
4. D.Jest snapshot tests

10. Remote image does not appear

A React Native screen renders `<Image source={{ uri: avatarUrl }} />` and nothing shows, with no error. What is the most likely cause?

1. A.Network images need an explicit width and height in the style
2. B.Remote images only load when Hermes is disabled
3. C.Images must be in the GIF format to load from a URL
4. D.The Image component cannot load https addresses

11. Expo Go and custom native code

An Expo app adds a library with its own native code, and it fails inside the Expo Go app. What is the usual fix?

1. A.Create a development build that includes the native code
2. B.Reinstall Expo Go from the store on the same phone
3. C.Move the library import inside a try and catch block
4. D.Switch the project from TypeScript to JavaScript

12. React Native New Architecture

What is a key benefit of the React Native New Architecture (JSI, Fabric and TurboModules), which is the default in recent versions?

1. A.It compiles JavaScript directly to Swift and Kotlin
2. B.It removes the need for any native code
3. C.JavaScript can call native code directly through JSI instead of sending async JSON messages over the old bridge
4. D.It runs the app inside a WebView for better compatibility

13. Listener without effect cleanup

What is the problem with this React Native effect?

useEffect(() => {
  const sub = AppState.addEventListener('change', onChange)
}, [])

1. A.It never removes the listener; return () => sub.remove() so it is cleaned up when the component unmounts
2. B.useEffect cannot use AppState
3. C.The dependency array must contain AppState and onChange, otherwise the listener is never registered at all
4. D.addEventListener must be awaited

14. What expo prebuild does

An Expo project has no android or ios folders in Git. What does `npx expo prebuild` do?

1. A.Uploads the JavaScript bundle straight to the app stores
2. B.Deletes all native code so the app runs in Expo Go
3. C.Converts the project into a Flutter app
4. D.Generates native projects from the app config and plugins

15. What Fabric is

In the React Native New Architecture, what is Fabric?

1. A.The new JavaScript engine that replaces Hermes on Android
2. B.A cloud service for distributing OTA updates
3. C.The new renderer, with a shared C++ core for the UI tree
4. D.A styling library that replaces StyleSheet

16. What autolinking does

Why do you rarely need to edit MainApplication or Podfile by hand when adding a React Native library?

1. A.The library is compiled into the JS bundle by Metro itself
2. B.Autolinking finds native code in node_modules and wires it in
3. C.Hermes loads the native code at runtime from npm
4. D.Native modules are no longer allowed in React Native

17. Querying in React Native Testing Library

Which query best follows React Native Testing Library's guidance for finding a "Submit" button?

1. A.screen.getByRole('button', { name: 'Submit' })
2. B.wrapper.find('TouchableOpacity').at(2)
3. C.screen.UNSAFE_getByType(Pressable)
4. D.component.props.children[3]

18. What Kotlin Multiplatform shares

How does Kotlin Multiplatform (KMP) typically differ from Flutter and React Native?

1. A.It shares only the UI and requires separate business logic
2. B.It shares business logic in Kotlin while each platform can keep native UI
3. C.It runs JavaScript on iOS through a Kotlin interpreter
4. D.It replaces Swift with Dart on Apple devices

19. React Native in a native app

What does "brownfield" React Native integration mean?

1. A.Adding React Native screens to an existing native iOS or Android app
2. B.Starting a new React Native app from the default template
3. C.Running React Native code on a smart TV platform
4. D.Moving a React Native app over to the Flutter framework

20. Shrinking a React Native Android app

A React Native Android app is 70 MB. Which step usually gives the biggest size reduction for users who install from Play?

1. A.Upload an App Bundle so Play sends only the needed ABI
2. B.Convert all of the PNG images to BMP format
3. C.Disable Hermes and ship the plain JavaScript source
4. D.Move every image into the JavaScript bundle

21. Unreadable JS stack traces in crashes

Crash reports from a release React Native build show stack frames like `index.android.bundle:1:84213`. What makes them readable?

1. A.Turning on remote JS debugging for release builds
2. B.Uploading the release source maps to the crash reporting tool
3. C.Logging every function name with console.log
4. D.Building the release with the debug flag set

22. Expo push token or FCM token

An Expo app gets a token from `getExpoPushTokenAsync()`. How is a push sent to that device?

1. A.Your server sends it directly to APNs with the Expo token
2. B.The device polls the Expo token endpoint every minute
3. C.Expo tokens only work for local notifications
4. D.Your server calls the Expo push service, which forwards to FCM or APNs

23. Pages that should expire

An event page for a Dubai expo should drop from Google after the event. Which robots rule fits?

1. A.unavailable_after with a date
2. B.noarchive with the event name
3. C.nosnippet on the event details
4. D.max-snippet set to zero

24. Animation stutters while data loads

A React Native card animation stutters whenever a large JSON response is parsed. What is the usual fix?

1. A.Run it on the UI thread (native driver or Reanimated)
2. B.Use setInterval to drive the animation each frame
3. C.Parse the JSON inside the animation callback instead
4. D.Increase the animation duration so it hides the lag

25. Animation stutters while JS is busy

A React Native Animated fade stutters whenever the JS thread is busy parsing a large response. Why, and what is the fix?

1. A.The animation is driven frame by frame from the JS thread; use useNativeDriver: true for opacity and transform, or Reanimated worklets that run on the UI thread
2. B.Hermes pauses timers while it parses JSON, so switching the engine to JavaScriptCore lets the Animated timing keep running during parsing
3. C.Call setState more often so the animation keeps up
4. D.Animations always stutter in React Native and nothing can fix it

26. OTA update crashes older installs

An OTA update that uses a new native library crashes users who still run the previous store build. What prevents this?

1. A.A runtimeVersion that changes with native code changes
2. B.Publishing the update twice so that both builds receive it
3. C.Shipping the update with a larger JavaScript bundle
4. D.Disabling Hermes so the bundle can load any library

27. Turbo Modules and Codegen

In the React Native New Architecture, what does Codegen do for a Turbo Module?

1. A.Converts the native module into pure JavaScript code
2. B.Bundles the module into the Hermes bytecode file itself
3. C.Creates a REST API that the module can call
4. D.Generates typed native glue from a TypeScript module spec

28. Bridgeless mode in React Native

React Native 0.74 and later run in "bridgeless" mode under the New Architecture. What does that mean?

1. A.The app no longer contains any native code at all
2. B.JavaScript runs on the UI thread with no separate JS thread
3. C.All native modules are removed and must be rewritten in JS
4. D.The legacy async bridge is not started; calls go through JSI

29. Reading the React Native perf monitor

The perf monitor shows UI at 60 fps but JS at 8 fps while a list is scrolling. What does this tell you?

1. A.The GPU is overloaded and native views are dropping frames
2. B.The device is low on storage space for the app
3. C.The JS thread is overloaded, so touches and updates driven by JS will lag
4. D.Hermes is disabled and JS is being interpreted

30. Metro cannot find a shared package

In a monorepo, the React Native app imports `@acme/ui` from packages/ui, but Metro reports it cannot resolve the module. What is a common fix?

1. A.Copy the shared package into the app's src folder by hand
2. B.Publish the package to npm before every local change
3. C.Configure Metro's watchFolders and node_modules paths for the workspace
4. D.Run the app with Hermes disabled for that package