Top 30 React Native Sollicitatievragen: Volledige Gids 2026

De 30 meest gestelde React Native sollicitatievragen. Gedetailleerde antwoorden met codevoorbeelden om de baan als mobile developer te bemachtigen.

Illustratie van React Native-sollicitatievragen met onderling verbonden mobiele componenten

Technische sollicitatiegesprekken over React Native peilen naar cross-platform mobiele ontwikkelvaardigheden, iOS- en Android-specifieke kennis en performance-patronen. Deze gids behandelt de 30 meest gestelde vragen, met gedetailleerde antwoorden en codevoorbeelden voor een effectieve voorbereiding.

Tip voor de voorbereiding

Deze vragen lopen van de basis tot gevorderde concepten. Het beheersen van de React Native-architectuur en het begrijpen van de verschillen met React Web zijn cruciaal om het gesprek tot een goed einde te brengen.

React Native Fundamenten

1. Wat is het verschil tussen React en React Native?

React is een library voor het bouwen van webinterfaces, terwijl React Native native mobiele app-ontwikkeling voor iOS en Android mogelijk maakt.

Het fundamentele verschil zit in de rendering: React gebruikt een Virtual DOM die naar HTML-elementen vertaalt, terwijl React Native een bridge inzet die met de native componenten van elk platform communiceert.

jsx
// React (Web) - uses HTML elements
function WebComponent() {
  return (
    <div className="container">
      <span>Web text</span>
      <button onClick={handleClick}>Click</button>
    </div>
  )
}

// React Native - uses native components
import { View, Text, TouchableOpacity, StyleSheet } from 'react-native'

function NativeComponent() {
  return (
    <View style={styles.container}>
      <Text>Native text</Text>
      <TouchableOpacity onPress={handlePress}>
        <Text>Press</Text>
      </TouchableOpacity>
    </View>
  )
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    padding: 16
  }
})

React Native-componenten worden op iOS vertaald naar UIView en op Android naar android.view, wat native performance oplevert.

2. Hoe werkt de architectuur van React Native?

React Native gebruikt een drielagige architectuur: JavaScript, Bridge (of JSI in de nieuwe architectuur) en Native.

De JavaScript-code draait in een JS-engine (Hermes of JavaScriptCore). De communicatie met native code verloopt in de oude architectuur via JSON-serialisatie, en in de nieuwe architectuur via JSI (JavaScript Interface).

jsx
// Old architecture: asynchronous communication via Bridge
// The Bridge serializes messages as JSON between JS and Native

// New architecture (Fabric + TurboModules)
// JSI enables synchronous direct calls to native modules

// Example TurboModule usage
import { TurboModuleRegistry } from 'react-native'

// Synchronous access to native module
const DeviceInfo = TurboModuleRegistry.get('DeviceInfo')
const deviceName = DeviceInfo.getDeviceName() // Synchronous call

// With Fabric, rendering is smoother
// Components can be created synchronously
// Reducing jank during animations

De nieuwe architectuur verbetert de performance aanzienlijk door JSON-serialisatie weg te nemen en synchrone aanroepen mogelijk te maken.

3. Wat is de Metro bundler?

Metro is de JavaScript-bundler die door React Native wordt gebruikt. Hij zet broncode om in een geoptimaliseerde bundle voor mobiele uitvoering.

Metro regelt module resolution, code-transformatie (via Babel) en hot reloading tijdens development.

metro.config.jsjavascript
const { getDefaultConfig } = require('expo/metro-config')

const config = getDefaultConfig(__dirname)

// Custom configuration
config.resolver.assetExts.push('db') // Add extensions
config.resolver.sourceExts.push('cjs') // CommonJS support

// Transformer configuration
config.transformer.babelTransformerPath = require.resolve(
  'react-native-svg-transformer'
)

// Production optimizations
config.transformer.minifierConfig = {
  keep_classnames: true,
  keep_fnames: true,
  mangle: {
    keep_classnames: true,
    keep_fnames: true
  }
}

module.exports = config

Metro ondersteunt Fast Refresh, waardoor wijzigingen direct zichtbaar zijn zonder dat de app-state verloren gaat.

4. Leg StyleSheet.create uit en zijn voordelen

StyleSheet.create optimaliseert stijlen door ze te valideren en om te zetten in numerieke verwijzingen, waardoor de overhead van de bridge afneemt.

jsx
// ❌ Inline styles - recreated on every render
function BadExample() {
  return (
    <View style={{ flex: 1, padding: 16, backgroundColor: '#fff' }}>
      <Text style={{ fontSize: 18, fontWeight: 'bold' }}>Title</Text>
    </View>
  )
}

// ✅ StyleSheet.create - optimized and validated
const styles = StyleSheet.create({
  container: {
    flex: 1,
    padding: 16,
    backgroundColor: '#fff'
  },
  title: {
    fontSize: 18,
    fontWeight: 'bold'
  },
  // Style composition
  row: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: 8
  }
})

function GoodExample() {
  return (
    <View style={styles.container}>
      <Text style={styles.title}>Title</Text>
      {/* Style combination */}
      <View style={[styles.row, { marginTop: 10 }]}>
        <Text>Content</Text>
      </View>
    </View>
  )
}

// StyleSheet.absoluteFillObject for absolute positioning
const overlayStyles = StyleSheet.create({
  overlay: {
    ...StyleSheet.absoluteFillObject,
    backgroundColor: 'rgba(0,0,0,0.5)'
  }
})

5. Wat is het verschil tussen Flexbox op het web en in React Native?

React Native gebruikt Flexbox, maar met andere standaardwaarden dan op het web, afgestemd op verticale mobiele interfaces.

jsx
// Key differences from web
const styles = StyleSheet.create({
  container: {
    // flexDirection: 'column' by default (vs 'row' on web)
    // alignItems: 'stretch' by default
    flex: 1
  },

  // React Native Flexbox
  row: {
    flexDirection: 'row',    // Horizontal
    justifyContent: 'space-between', // Main axis
    alignItems: 'center',    // Cross axis
    flexWrap: 'wrap',        // Line wrapping
    gap: 8                   // Supported since RN 0.71
  },

  // Flex grow/shrink
  flexItem: {
    flex: 1,        // Equivalent to flex: 1 1 0
    flexGrow: 1,    // Grow to fill
    flexShrink: 0,  // Don't shrink
    flexBasis: 100  // Base size
  },

  // Absolute positioning
  absolute: {
    position: 'absolute',
    top: 0,
    left: 0,
    right: 0,
    bottom: 0
  }
})

// Practical example: card with image and content
function Card() {
  return (
    <View style={cardStyles.container}>
      <Image source={{ uri: imageUrl }} style={cardStyles.image} />
      <View style={cardStyles.content}>
        <Text style={cardStyles.title}>Title</Text>
        <Text style={cardStyles.description}>Description</Text>
      </View>
    </View>
  )
}

const cardStyles = StyleSheet.create({
  container: {
    flexDirection: 'row',
    backgroundColor: '#fff',
    borderRadius: 8,
    overflow: 'hidden'
  },
  image: {
    width: 100,
    height: 100
  },
  content: {
    flex: 1, // Takes remaining space
    padding: 12,
    justifyContent: 'center'
  },
  title: {
    fontSize: 16,
    fontWeight: '600'
  },
  description: {
    fontSize: 14,
    color: '#666'
  }
})

6. Hoe implementeer je navigatie met React Navigation?

React Navigation is de standaardoplossing voor navigatie in React Native. De library biedt verschillende navigatortypes die aansluiten op mobiele patronen.

jsx
// Installing dependencies
// npm install @react-navigation/native @react-navigation/native-stack
// npm install react-native-screens react-native-safe-area-context

import { NavigationContainer } from '@react-navigation/native'
import { createNativeStackNavigator } from '@react-navigation/native-stack'
import { createBottomTabNavigator } from '@react-navigation/bottom-tabs'

// TypeScript typing for navigation params
type RootStackParamList = {
  Home: undefined
  Profile: { userId: string }
  Settings: { section?: string }
}

const Stack = createNativeStackNavigator<RootStackParamList>()
const Tab = createBottomTabNavigator()

// Tab navigation
function TabNavigator() {
  return (
    <Tab.Navigator
      screenOptions={({ route }) => ({
        tabBarIcon: ({ focused, color, size }) => {
          // Dynamic icon based on tab
          const iconName = route.name === 'Home' ? 'home' : 'settings'
          return <Icon name={iconName} size={size} color={color} />
        },
        tabBarActiveTintColor: '#007AFF',
        tabBarInactiveTintColor: 'gray'
      })}
    >
      <Tab.Screen name="Home" component={HomeScreen} />
      <Tab.Screen name="Settings" component={SettingsScreen} />
    </Tab.Navigator>
  )
}

// Stack navigation
function App() {
  return (
    <NavigationContainer>
      <Stack.Navigator
        initialRouteName="Home"
        screenOptions={{
          headerStyle: { backgroundColor: '#007AFF' },
          headerTintColor: '#fff',
          animation: 'slide_from_right' // Native animation
        }}
      >
        <Stack.Screen
          name="Home"
          component={TabNavigator}
          options={{ headerShown: false }}
        />
        <Stack.Screen
          name="Profile"
          component={ProfileScreen}
          options={({ route }) => ({
            title: `Profile ${route.params.userId}`
          })}
        />
      </Stack.Navigator>
    </NavigationContainer>
  )
}

7. Hoe beheer je performante lijsten met FlatList?

FlatList is geoptimaliseerd voor lange lijsten dankzij automatische virtualisatie en rendert alleen zichtbare elementen.

jsx
import { FlatList, RefreshControl } from 'react-native'

function ProductList() {
  const [products, setProducts] = useState([])
  const [refreshing, setRefreshing] = useState(false)
  const [loading, setLoading] = useState(false)

  // Initial loading
  const fetchProducts = async (page = 1) => {
    const response = await api.getProducts(page)
    return response.data
  }

  // Pull-to-refresh
  const onRefresh = useCallback(async () => {
    setRefreshing(true)
    const data = await fetchProducts(1)
    setProducts(data)
    setRefreshing(false)
  }, [])

  // Infinite pagination
  const loadMore = useCallback(async () => {
    if (loading) return
    setLoading(true)
    const nextPage = Math.ceil(products.length / 20) + 1
    const data = await fetchProducts(nextPage)
    setProducts(prev => [...prev, ...data])
    setLoading(false)
  }, [products.length, loading])

  // Item rendering
  const renderItem = useCallback(({ item }) => (
    <ProductCard product={item} />
  ), [])

  // Key extraction
  const keyExtractor = useCallback((item) => item.id.toString(), [])

  // Item separator
  const ItemSeparator = useCallback(() => (
    <View style={{ height: 12 }} />
  ), [])

  return (
    <FlatList
      data={products}
      renderItem={renderItem}
      keyExtractor={keyExtractor}
      ItemSeparatorComponent={ItemSeparator}
      // Performance optimizations
      removeClippedSubviews={true}
      maxToRenderPerBatch={10}
      updateCellsBatchingPeriod={50}
      windowSize={5}
      // Pull-to-refresh
      refreshControl={
        <RefreshControl
          refreshing={refreshing}
          onRefresh={onRefresh}
          tintColor="#007AFF"
        />
      }
      // Infinite pagination
      onEndReached={loadMore}
      onEndReachedThreshold={0.5}
      ListFooterComponent={loading ? <ActivityIndicator /> : null}
      // Empty list
      ListEmptyComponent={<EmptyState message="No products" />}
    />
  )
}
FlatList-optimalisatie

Memoiseer renderItem altijd met useCallback en haal zware componenten naar buiten. Vermijd inline-functies in renderItem die onnodige re-renders veroorzaken.

8. Wat is het verschil tussen TouchableOpacity, Pressable en TouchableHighlight?

Deze componenten verwerken aanraakinteracties met verschillende visuele feedback.

jsx
import {
  TouchableOpacity,
  TouchableHighlight,
  Pressable,
  StyleSheet
} from 'react-native'

function InteractionExamples() {
  return (
    <View style={styles.container}>
      {/* TouchableOpacity: reduces opacity on touch */}
      <TouchableOpacity
        activeOpacity={0.7}
        onPress={() => console.log('Pressed')}
        style={styles.button}
      >
        <Text>TouchableOpacity</Text>
      </TouchableOpacity>

      {/* TouchableHighlight: adds background color */}
      <TouchableHighlight
        underlayColor="#ddd"
        onPress={() => console.log('Pressed')}
        style={styles.button}
      >
        <Text>TouchableHighlight</Text>
      </TouchableHighlight>

      {/* Pressable: modern API with more control */}
      <Pressable
        onPress={() => console.log('Pressed')}
        onLongPress={() => console.log('Long press')}
        delayLongPress={500}
        style={({ pressed }) => [
          styles.button,
          pressed && styles.buttonPressed
        ]}
      >
        {({ pressed }) => (
          <Text style={pressed && styles.textPressed}>
            {pressed ? 'Pressed!' : 'Pressable'}
          </Text>
        )}
      </Pressable>

      {/* Pressable with hitSlop to enlarge touch area */}
      <Pressable
        hitSlop={{ top: 10, bottom: 10, left: 10, right: 10 }}
        onPress={() => console.log('Pressed')}
        style={styles.smallButton}
      >
        <Text>Small button</Text>
      </Pressable>
    </View>
  )
}

const styles = StyleSheet.create({
  container: {
    gap: 16,
    padding: 20
  },
  button: {
    backgroundColor: '#007AFF',
    padding: 16,
    borderRadius: 8,
    alignItems: 'center'
  },
  buttonPressed: {
    backgroundColor: '#0056b3',
    transform: [{ scale: 0.98 }]
  },
  textPressed: {
    color: '#fff'
  },
  smallButton: {
    padding: 8,
    backgroundColor: '#eee'
  }
})

Voor nieuwe projecten verdient Pressable de voorkeur, omdat het meer controle en een consistentere API biedt.

9. Hoe maak je vloeiende animaties?

React Native biedt meerdere animatie-API's: Animated (ingebouwd) en Reanimated (performanter).

jsx
import { Animated, Easing } from 'react-native'
import Reanimated, {
  useSharedValue,
  useAnimatedStyle,
  withSpring,
  withTiming
} from 'react-native-reanimated'

// Animation with Animated (native API)
function FadeInView({ children }) {
  const fadeAnim = useRef(new Animated.Value(0)).current

  useEffect(() => {
    Animated.timing(fadeAnim, {
      toValue: 1,
      duration: 500,
      easing: Easing.ease,
      useNativeDriver: true // Performant on UI thread
    }).start()
  }, [])

  return (
    <Animated.View style={{ opacity: fadeAnim }}>
      {children}
    </Animated.View>
  )
}

// Animation with Reanimated (recommended for complex animations)
function BouncyButton() {
  const scale = useSharedValue(1)

  const animatedStyle = useAnimatedStyle(() => ({
    transform: [{ scale: scale.value }]
  }))

  const handlePressIn = () => {
    scale.value = withSpring(0.95, {
      damping: 10,
      stiffness: 400
    })
  }

  const handlePressOut = () => {
    scale.value = withSpring(1, {
      damping: 10,
      stiffness: 400
    })
  }

  return (
    <Pressable onPressIn={handlePressIn} onPressOut={handlePressOut}>
      <Reanimated.View style={[styles.button, animatedStyle]}>
        <Text style={styles.buttonText}>Press</Text>
      </Reanimated.View>
    </Pressable>
  )
}

// List animation with LayoutAnimation
import { LayoutAnimation, UIManager, Platform } from 'react-native'

// Enable on Android
if (Platform.OS === 'android') {
  UIManager.setLayoutAnimationEnabledExperimental?.(true)
}

function AnimatedList() {
  const [items, setItems] = useState([])

  const addItem = () => {
    // Configure animation before state change
    LayoutAnimation.configureNext(LayoutAnimation.Presets.spring)
    setItems(prev => [...prev, { id: Date.now() }])
  }

  const removeItem = (id) => {
    LayoutAnimation.configureNext(LayoutAnimation.Presets.easeInEaseOut)
    setItems(prev => prev.filter(item => item.id !== id))
  }

  return (
    <View>
      <Button title="Add" onPress={addItem} />
      {items.map(item => (
        <TouchableOpacity key={item.id} onPress={() => removeItem(item.id)}>
          <View style={styles.item}>
            <Text>Item {item.id}</Text>
          </View>
        </TouchableOpacity>
      ))}
    </View>
  )
}

Klaar om je React Native gesprekken te halen?

Oefen met onze interactieve simulatoren, flashcards en technische tests.

State en databeheer

10. Hoe beheer je globale state in React Native?

Dezelfde oplossingen als voor React Web zijn van toepassing: Context API, Redux, Zustand of MobX.

jsx
// Lightweight solution with Zustand
import { create } from 'zustand'
import { persist, createJSONStorage } from 'zustand/middleware'
import AsyncStorage from '@react-native-async-storage/async-storage'

// Store with persistence
const useAuthStore = create(
  persist(
    (set, get) => ({
      user: null,
      token: null,
      isAuthenticated: false,

      login: async (email, password) => {
        const response = await api.login(email, password)
        set({
          user: response.user,
          token: response.token,
          isAuthenticated: true
        })
      },

      logout: () => {
        set({ user: null, token: null, isAuthenticated: false })
      },

      updateProfile: (updates) => {
        set(state => ({
          user: { ...state.user, ...updates }
        }))
      }
    }),
    {
      name: 'auth-storage',
      storage: createJSONStorage(() => AsyncStorage)
    }
  )
)

// Usage in a component
function ProfileScreen() {
  const { user, logout, updateProfile } = useAuthStore()

  if (!user) return <LoginPrompt />

  return (
    <View style={styles.container}>
      <Text style={styles.name}>{user.name}</Text>
      <Text style={styles.email}>{user.email}</Text>

      <TouchableOpacity onPress={logout} style={styles.logoutButton}>
        <Text>Logout</Text>
      </TouchableOpacity>
    </View>
  )
}

// Cart store
const useCartStore = create((set, get) => ({
  items: [],

  addItem: (product) => set(state => {
    const existing = state.items.find(i => i.id === product.id)
    if (existing) {
      return {
        items: state.items.map(i =>
          i.id === product.id
            ? { ...i, quantity: i.quantity + 1 }
            : i
        )
      }
    }
    return { items: [...state.items, { ...product, quantity: 1 }] }
  }),

  removeItem: (id) => set(state => ({
    items: state.items.filter(i => i.id !== id)
  })),

  getTotal: () => {
    return get().items.reduce(
      (sum, item) => sum + item.price * item.quantity,
      0
    )
  },

  clearCart: () => set({ items: [] })
}))

11. Hoe doe je API-aanroepen met cachebeheer?

React Query (TanStack Query) is de aanbevolen oplossing voor het beheren van serverdata.

jsx
import { QueryClient, QueryClientProvider, useQuery, useMutation } from '@tanstack/react-query'

// Client configuration
const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      staleTime: 5 * 60 * 1000, // 5 minutes
      cacheTime: 30 * 60 * 1000, // 30 minutes
      retry: 2,
      refetchOnWindowFocus: false // Mobile doesn't have "window focus"
    }
  }
})

// Provider in App.tsx
function App() {
  return (
    <QueryClientProvider client={queryClient}>
      <NavigationContainer>
        <AppNavigator />
      </NavigationContainer>
    </QueryClientProvider>
  )
}

// Custom hook for products
function useProducts(categoryId) {
  return useQuery({
    queryKey: ['products', categoryId],
    queryFn: async () => {
      const response = await fetch(`/api/products?category=${categoryId}`)
      if (!response.ok) throw new Error('Network error')
      return response.json()
    },
    enabled: !!categoryId // Don't execute if no categoryId
  })
}

// Mutation with cache invalidation
function useAddToCart() {
  const queryClient = useQueryClient()

  return useMutation({
    mutationFn: async (product) => {
      const response = await fetch('/api/cart', {
        method: 'POST',
        body: JSON.stringify(product)
      })
      return response.json()
    },
    onSuccess: () => {
      // Invalidate cart cache to force refetch
      queryClient.invalidateQueries({ queryKey: ['cart'] })
    },
    onError: (error) => {
      Alert.alert('Error', error.message)
    }
  })
}

// Usage in a component
function ProductListScreen({ categoryId }) {
  const { data: products, isLoading, error, refetch } = useProducts(categoryId)
  const addToCart = useAddToCart()

  if (isLoading) return <LoadingSpinner />
  if (error) return <ErrorView error={error} onRetry={refetch} />

  return (
    <FlatList
      data={products}
      renderItem={({ item }) => (
        <ProductCard
          product={item}
          onAddToCart={() => addToCart.mutate(item)}
          isAddingToCart={addToCart.isPending}
        />
      )}
      refreshing={isLoading}
      onRefresh={refetch}
    />
  )
}

12. Hoe sla je gegevens lokaal op?

Afhankelijk van het type data zijn er meerdere opties: AsyncStorage voor eenvoudige data, MMKV voor performance en SQLite voor gestructureerde data.

jsx
// AsyncStorage - simple but slow for large volumes
import AsyncStorage from '@react-native-async-storage/async-storage'

const storage = {
  async get(key) {
    const value = await AsyncStorage.getItem(key)
    return value ? JSON.parse(value) : null
  },

  async set(key, value) {
    await AsyncStorage.setItem(key, JSON.stringify(value))
  },

  async remove(key) {
    await AsyncStorage.removeItem(key)
  },

  async clear() {
    await AsyncStorage.clear()
  }
}

// MMKV - very performant (recommended)
import { MMKV } from 'react-native-mmkv'

const mmkv = new MMKV()

const fastStorage = {
  get(key) {
    const value = mmkv.getString(key)
    return value ? JSON.parse(value) : null
  },

  set(key, value) {
    mmkv.set(key, JSON.stringify(value))
  },

  remove(key) {
    mmkv.delete(key)
  },

  // Primitive type support
  getNumber(key) {
    return mmkv.getNumber(key)
  },

  setNumber(key, value) {
    mmkv.set(key, value)
  },

  getBoolean(key) {
    return mmkv.getBoolean(key)
  }
}

// Hook to use MMKV with React
function useMMKVStorage(key, defaultValue) {
  const [value, setValue] = useState(() => {
    const stored = fastStorage.get(key)
    return stored ?? defaultValue
  })

  const setStoredValue = useCallback((newValue) => {
    setValue(newValue)
    fastStorage.set(key, newValue)
  }, [key])

  return [value, setStoredValue]
}

// Usage
function SettingsScreen() {
  const [theme, setTheme] = useMMKVStorage('theme', 'light')
  const [notifications, setNotifications] = useMMKVStorage('notifications', true)

  return (
    <View>
      <Switch
        value={theme === 'dark'}
        onValueChange={(v) => setTheme(v ? 'dark' : 'light')}
      />
      <Switch
        value={notifications}
        onValueChange={setNotifications}
      />
    </View>
  )
}
Gevoelige data

Voor tokens en gevoelige data zijn expo-secure-store of react-native-keychain geschikt; deze versleutelen data via Keychain (iOS) en Keystore (Android).

Performance en optimalisatie

13. Hoe optimaliseer je de performance van een React Native-app?

De optimalisatie raakt meerdere aspecten: rendering, geheugen en interacties.

1. Avoid unnecessary re-renders with React.memojsx
const ProductCard = React.memo(function ProductCard({ product, onPress }) {
  return (
    <TouchableOpacity onPress={() => onPress(product.id)}>
      <View style={styles.card}>
        <Image source={{ uri: product.image }} style={styles.image} />
        <Text style={styles.title}>{product.name}</Text>
        <Text style={styles.price}>{product.price}$</Text>
      </View>
    </TouchableOpacity>
  )
}, (prevProps, nextProps) => {
  // Custom comparison
  return prevProps.product.id === nextProps.product.id
})

// 2. Memoize callbacks
function ProductList({ products }) {
  // ❌ New function on every render
  // onPress={(id) => handlePress(id)}

  // ✅ Stable function
  const handlePress = useCallback((id) => {
    navigation.navigate('Product', { id })
  }, [navigation])

  return (
    <FlatList
      data={products}
      renderItem={({ item }) => (
        <ProductCard product={item} onPress={handlePress} />
      )}
    />
  )
}

// 3. Optimize images
import FastImage from 'react-native-fast-image'

function OptimizedImage({ uri }) {
  return (
    <FastImage
      source={{
        uri,
        priority: FastImage.priority.normal,
        cache: FastImage.cacheControl.immutable
      }}
      style={styles.image}
      resizeMode={FastImage.resizeMode.cover}
    />
  )
}

// 4. Use InteractionManager for heavy tasks
import { InteractionManager } from 'react-native'

function HeavyScreen() {
  const [data, setData] = useState(null)

  useEffect(() => {
    // Wait for animations to complete
    const task = InteractionManager.runAfterInteractions(() => {
      const result = performHeavyComputation()
      setData(result)
    })

    return () => task.cancel()
  }, [])

  return data ? <DataView data={data} /> : <LoadingView />
}

// 5. Lazy loading screens
const HeavyScreen = React.lazy(() => import('./HeavyScreen'))

function Navigator() {
  return (
    <Stack.Navigator>
      <Stack.Screen
        name="Heavy"
        component={HeavyScreen}
        options={{ lazy: true }}
      />
    </Stack.Navigator>
  )
}

14. Hoe debug je performance-problemen?

React Native biedt verschillende tools om bottlenecks op te sporen.

1. Flipper - main debugging tooljsx
// Configuration in android/app/build.gradle and ios/Podfile
// See: https://fbflipper.com/

// 2. Console.time to measure operations
function fetchData() {
  console.time('fetchData')
  const data = await api.getData()
  console.timeEnd('fetchData') // fetchData: 234ms
  return data
}

// 3. Performance monitor (shake device → Show Perf Monitor)
// Shows JS and UI FPS

// 4. Hermes profiler for CPU
// Enable in metro.config.js
module.exports = {
  transformer: {
    hermesParser: true
  }
}

// 5. Identify re-renders with why-did-you-render
// Installation: npm install @welldone-software/why-did-you-render
import React from 'react'

if (__DEV__) {
  const whyDidYouRender = require('@welldone-software/why-did-you-render')
  whyDidYouRender(React, {
    trackAllPureComponents: true
  })
}

// Mark a component to monitor
ProductCard.whyDidYouRender = true

// 6. Measure mount time
function useComponentTiming(componentName) {
  const mountTime = useRef(Date.now())

  useEffect(() => {
    const duration = Date.now() - mountTime.current
    console.log(`${componentName} mounted in ${duration}ms`)

    return () => {
      console.log(`${componentName} unmounted`)
    }
  }, [componentName])
}

// Usage
function MyComponent() {
  useComponentTiming('MyComponent')
  // ...
}

15. Hoe ga je om met de offline-modus?

Offline-werking vereist een caching- en synchronisatiestrategie.

jsx
import NetInfo from '@react-native-community/netinfo'

// Hook to monitor connectivity
function useNetworkStatus() {
  const [isConnected, setIsConnected] = useState(true)
  const [connectionType, setConnectionType] = useState(null)

  useEffect(() => {
    const unsubscribe = NetInfo.addEventListener(state => {
      setIsConnected(state.isConnected)
      setConnectionType(state.type)
    })

    return () => unsubscribe()
  }, [])

  return { isConnected, connectionType }
}

// Service with offline queue
class OfflineQueue {
  constructor() {
    this.queue = []
    this.isProcessing = false
  }

  async add(action) {
    this.queue.push({
      id: Date.now(),
      action,
      timestamp: new Date().toISOString()
    })
    await this.persist()
  }

  async persist() {
    await AsyncStorage.setItem('offline_queue', JSON.stringify(this.queue))
  }

  async load() {
    const data = await AsyncStorage.getItem('offline_queue')
    this.queue = data ? JSON.parse(data) : []
  }

  async process() {
    if (this.isProcessing || this.queue.length === 0) return

    this.isProcessing = true
    const { isConnected } = await NetInfo.fetch()

    if (!isConnected) {
      this.isProcessing = false
      return
    }

    while (this.queue.length > 0) {
      const item = this.queue[0]
      try {
        await this.executeAction(item.action)
        this.queue.shift()
        await this.persist()
      } catch (error) {
        console.error('Failed to process action:', error)
        break
      }
    }

    this.isProcessing = false
  }

  async executeAction(action) {
    switch (action.type) {
      case 'CREATE_ORDER':
        return api.createOrder(action.payload)
      case 'UPDATE_PROFILE':
        return api.updateProfile(action.payload)
      default:
        throw new Error(`Unknown action: ${action.type}`)
    }
  }
}

const offlineQueue = new OfflineQueue()

// Network status banner component
function NetworkBanner() {
  const { isConnected } = useNetworkStatus()

  if (isConnected) return null

  return (
    <View style={styles.banner}>
      <Text style={styles.bannerText}>
        Offline mode - Changes will be synchronized
      </Text>
    </View>
  )
}

Mobiele specificiteiten

16. Hoe beheer je permissies op iOS en Android?

Permissies worden op elk platform anders afgehandeld. Libraries zoals react-native-permissions uniformeren de API.

jsx
import { Platform, Alert, Linking } from 'react-native'
import {
  check,
  request,
  PERMISSIONS,
  RESULTS,
  openSettings
} from 'react-native-permissions'

// Permission configuration per platform
const PERMISSION_TYPES = {
  camera: Platform.select({
    ios: PERMISSIONS.IOS.CAMERA,
    android: PERMISSIONS.ANDROID.CAMERA
  }),
  photos: Platform.select({
    ios: PERMISSIONS.IOS.PHOTO_LIBRARY,
    android: PERMISSIONS.ANDROID.READ_MEDIA_IMAGES
  }),
  location: Platform.select({
    ios: PERMISSIONS.IOS.LOCATION_WHEN_IN_USE,
    android: PERMISSIONS.ANDROID.ACCESS_FINE_LOCATION
  })
}

// Hook to manage permissions
function usePermission(type) {
  const [status, setStatus] = useState(RESULTS.UNAVAILABLE)

  const permission = PERMISSION_TYPES[type]

  useEffect(() => {
    check(permission).then(setStatus)
  }, [permission])

  const requestPermission = useCallback(async () => {
    const result = await request(permission)
    setStatus(result)

    if (result === RESULTS.BLOCKED) {
      Alert.alert(
        'Permission required',
        `This feature requires ${type} access. Do you want to open settings?`,
        [
          { text: 'No', style: 'cancel' },
          { text: 'Open', onPress: openSettings }
        ]
      )
    }

    return result
  }, [permission, type])

  return {
    status,
    isGranted: status === RESULTS.GRANTED,
    isDenied: status === RESULTS.DENIED,
    isBlocked: status === RESULTS.BLOCKED,
    requestPermission
  }
}

// Usage
function CameraButton() {
  const { isGranted, requestPermission } = usePermission('camera')

  const handlePress = async () => {
    if (!isGranted) {
      const result = await requestPermission()
      if (result !== RESULTS.GRANTED) return
    }
    // Open camera
    navigation.navigate('Camera')
  }

  return (
    <TouchableOpacity onPress={handlePress}>
      <Text>Take a photo</Text>
    </TouchableOpacity>
  )
}

17. Hoe implementeer je push-notificaties?

Push-notificaties vragen om native configuratie en een backend voor de verzending.

jsx
import messaging from '@react-native-firebase/messaging'
import notifee, { AndroidImportance } from '@notifee/react-native'

// Notification service
class NotificationService {
  async initialize() {
    // Request permission (iOS)
    const authStatus = await messaging().requestPermission()
    const enabled = authStatus === messaging.AuthorizationStatus.AUTHORIZED

    if (enabled) {
      // Get FCM token
      const token = await messaging().getToken()
      await this.registerToken(token)

      // Listen for token changes
      messaging().onTokenRefresh(this.registerToken)

      // Create Android channel
      await notifee.createChannel({
        id: 'default',
        name: 'Notifications',
        importance: AndroidImportance.HIGH
      })
    }

    return enabled
  }

  async registerToken(token) {
    // Send token to backend
    await api.registerPushToken(token)
  }

  // Setup handlers
  setupHandlers() {
    // Notification received in foreground
    messaging().onMessage(async (remoteMessage) => {
      await this.displayNotification(remoteMessage)
    })

    // Notification tapped (app in background)
    messaging().onNotificationOpenedApp((remoteMessage) => {
      this.handleNotificationPress(remoteMessage)
    })

    // App opened from notification (app closed)
    messaging()
      .getInitialNotification()
      .then((remoteMessage) => {
        if (remoteMessage) {
          this.handleNotificationPress(remoteMessage)
        }
      })
  }

  async displayNotification(remoteMessage) {
    const { title, body } = remoteMessage.notification

    await notifee.displayNotification({
      title,
      body,
      android: {
        channelId: 'default',
        pressAction: { id: 'default' }
      },
      data: remoteMessage.data
    })
  }

  handleNotificationPress(remoteMessage) {
    const { type, id } = remoteMessage.data

    switch (type) {
      case 'order':
        navigation.navigate('OrderDetail', { orderId: id })
        break
      case 'message':
        navigation.navigate('Chat', { conversationId: id })
        break
    }
  }
}

// Usage in App.tsx
function App() {
  useEffect(() => {
    const notificationService = new NotificationService()
    notificationService.initialize()
    notificationService.setupHandlers()
  }, [])

  return <AppNavigator />
}

Deep links maken het mogelijk om de app op een specifiek scherm te openen vanuit een externe URL.

jsx
import { Linking } from 'react-native'
import { NavigationContainer } from '@react-navigation/native'

// Deep link configuration
const linking = {
  prefixes: ['myapp://', 'https://myapp.com'],

  config: {
    screens: {
      Home: 'home',
      Product: {
        path: 'product/:id',
        parse: {
          id: (id) => parseInt(id, 10)
        }
      },
      Profile: 'profile/:userId?',
      Settings: {
        path: 'settings',
        screens: {
          Notifications: 'notifications',
          Privacy: 'privacy'
        }
      }
    }
  },

  // Custom function to get initial URL
  async getInitialURL() {
    // Check if app was opened via deep link
    const url = await Linking.getInitialURL()
    if (url) return url

    // Check notifications
    const message = await messaging().getInitialNotification()
    if (message?.data?.link) return message.data.link

    return null
  },

  // Subscribe to incoming links
  subscribe(listener) {
    // Standard deep links
    const linkingSubscription = Linking.addEventListener('url', ({ url }) => {
      listener(url)
    })

    // Links from notifications
    const unsubscribeNotification = messaging().onNotificationOpenedApp(
      (message) => {
        const link = message.data?.link
        if (link) listener(link)
      }
    )

    return () => {
      linkingSubscription.remove()
      unsubscribeNotification()
    }
  }
}

// Usage
function App() {
  return (
    <NavigationContainer linking={linking} fallback={<LoadingScreen />}>
      <Stack.Navigator>
        <Stack.Screen name="Home" component={HomeScreen} />
        <Stack.Screen name="Product" component={ProductScreen} />
        <Stack.Screen name="Profile" component={ProfileScreen} />
      </Stack.Navigator>
    </NavigationContainer>
  )
}

// Testing deep links
// myapp://product/123
// https://myapp.com/profile/user456

Klaar om je React Native gesprekken te halen?

Oefen met onze interactieve simulatoren, flashcards en technische tests.

Native code en modules

19. Wanneer en hoe schrijf je native code?

Native code is nodig om functionaliteit te benaderen die niet in JavaScript beschikbaar is, of om kritieke performance te optimaliseren.

jsx
// iOS - Native module in Swift
// ios/MyModule.swift
import Foundation

@objc(MyModule)
class MyModule: NSObject {

  @objc
  func getDeviceInfo(_ resolve: @escaping RCTPromiseResolveBlock,
                     rejecter reject: @escaping RCTPromiseRejectBlock) {
    let info: [String: Any] = [
      "model": UIDevice.current.model,
      "systemVersion": UIDevice.current.systemVersion,
      "name": UIDevice.current.name
    ]
    resolve(info)
  }

  @objc
  static func requiresMainQueueSetup() -> Bool {
    return false
  }
}

// ios/MyModule.m (Bridge)
#import <React/RCTBridgeModule.h>

@interface RCT_EXTERN_MODULE(MyModule, NSObject)

RCT_EXTERN_METHOD(getDeviceInfo:(RCTPromiseResolveBlock)resolve
                  rejecter:(RCTPromiseRejectBlock)reject)

@end

// Android - Native module in Kotlin
// android/app/src/main/java/com/myapp/MyModule.kt
package com.myapp

import com.facebook.react.bridge.*

class MyModule(reactContext: ReactApplicationContext) :
    ReactContextBaseJavaModule(reactContext) {

    override fun getName() = "MyModule"

    @ReactMethod
    fun getDeviceInfo(promise: Promise) {
        val info = Arguments.createMap().apply {
            putString("model", android.os.Build.MODEL)
            putString("systemVersion", android.os.Build.VERSION.RELEASE)
            putString("manufacturer", android.os.Build.MANUFACTURER)
        }
        promise.resolve(info)
    }
}

// JavaScript - Using native module
import { NativeModules } from 'react-native'

const { MyModule } = NativeModules

async function getDeviceInfo() {
  try {
    const info = await MyModule.getDeviceInfo()
    console.log('Device info:', info)
    return info
  } catch (error) {
    console.error('Error getting device info:', error)
    throw error
  }
}

20. Wat is Expo en wanneer gebruik je het?

Expo is een framework dat React Native-ontwikkeling vereenvoudigt door de native configuratie uit handen te nemen.

jsx
// Expo benefits
// - No need for Android Studio or Xcode to start
// - OTA (over-the-air) updates without app stores
// - Rich SDK with preconfigured modules
// - EAS Build for cloud builds

// Creating an Expo project
// npx create-expo-app@latest MyApp

// Using Expo modules
import * as ImagePicker from 'expo-image-picker'
import * as Location from 'expo-location'
import * as Notifications from 'expo-notifications'

async function pickImage() {
  // Request permission
  const { status } = await ImagePicker.requestMediaLibraryPermissionsAsync()

  if (status !== 'granted') {
    alert('Permission denied')
    return
  }

  // Open image picker
  const result = await ImagePicker.launchImageLibraryAsync({
    mediaTypes: ImagePicker.MediaTypeOptions.Images,
    allowsEditing: true,
    aspect: [4, 3],
    quality: 0.8
  })

  if (!result.canceled) {
    return result.assets[0].uri
  }
}

// Build configuration
// app.json
{
  "expo": {
    "name": "MyApp",
    "slug": "myapp",
    "version": "1.0.0",
    "orientation": "portrait",
    "icon": "./assets/icon.png",
    "splash": {
      "image": "./assets/splash.png",
      "resizeMode": "contain",
      "backgroundColor": "#ffffff"
    },
    "ios": {
      "supportsTablet": true,
      "bundleIdentifier": "com.company.myapp"
    },
    "android": {
      "adaptiveIcon": {
        "foregroundImage": "./assets/adaptive-icon.png",
        "backgroundColor": "#ffffff"
      },
      "package": "com.company.myapp"
    },
    "plugins": [
      "expo-router",
      [
        "expo-camera",
        {
          "cameraPermission": "Allow camera access"
        }
      ]
    ]
  }
}

// When NOT to use Expo
// - Need for complex custom native modules
// - Integration with specific native SDKs
// - Total control over native configuration
// - Very lightweight application (Expo adds weight)

21. Hoe werkt Hot Reloading?

Hot Reloading (Fast Refresh) maakt directe wijzigingen mogelijk zonder verlies van de app-state.

jsx
// Fast Refresh preserves hooks state
function Counter() {
  const [count, setCount] = useState(0)

  // Modify this text and save
  // The count state will be preserved
  return (
    <View>
      <Text>Counter: {count}</Text>
      <Button title="+1" onPress={() => setCount(c => c + 1)} />
    </View>
  )
}

// ⚠️ Cases where Fast Refresh does full reload
// 1. Syntax error
// 2. Modifying a class component
// 3. File with mixed non-component exports

// ❌ This file will do full reload because of mixed exports
export const API_URL = 'https://api.example.com'
export function MyComponent() { /* ... */ }

// ✅ Separate into distinct files
// constants.js
export const API_URL = 'https://api.example.com'

// MyComponent.js
export function MyComponent() { /* ... */ }

// Force remount if needed
// Add this comment at top of file:
// @refresh reset

// Metro configuration for Fast Refresh
// metro.config.js
module.exports = {
  transformer: {
    experimentalImportSupport: false,
    inlineRequires: true
  }
}

Testen en kwaliteit

22. Hoe test je een React Native-applicatie?

Het testen in React Native gebeurt met Jest en gespecialiseerde libraries voor rendering en interacties.

jsx
// Jest configuration
// jest.config.js
module.exports = {
  preset: 'react-native',
  setupFilesAfterEnv: ['@testing-library/jest-native/extend-expect'],
  transformIgnorePatterns: [
    'node_modules/(?!(react-native|@react-native|@react-navigation)/)'
  ],
  moduleNameMapper: {
    '\\.(jpg|jpeg|png|gif|webp|svg)$': '<rootDir>/__mocks__/fileMock.js'
  }
}

// Component test with React Native Testing Library
import { render, screen, fireEvent, waitFor } from '@testing-library/react-native'
import { ProductCard } from './ProductCard'

describe('ProductCard', () => {
  const mockProduct = {
    id: '1',
    name: 'iPhone 15',
    price: 999,
    image: 'https://example.com/iphone.jpg'
  }

  it('renders product information', () => {
    render(<ProductCard product={mockProduct} />)

    expect(screen.getByText('iPhone 15')).toBeOnTheScreen()
    expect(screen.getByText('$999')).toBeOnTheScreen()
  })

  it('calls onPress when tapped', () => {
    const onPress = jest.fn()
    render(<ProductCard product={mockProduct} onPress={onPress} />)

    fireEvent.press(screen.getByTestId('product-card'))

    expect(onPress).toHaveBeenCalledWith('1')
  })

  it('shows loading state when adding to cart', async () => {
    const onAddToCart = jest.fn(() => new Promise(r => setTimeout(r, 100)))
    render(<ProductCard product={mockProduct} onAddToCart={onAddToCart} />)

    fireEvent.press(screen.getByText('Add to cart'))

    expect(screen.getByTestId('loading-indicator')).toBeOnTheScreen()

    await waitFor(() => {
      expect(screen.queryByTestId('loading-indicator')).not.toBeOnTheScreen()
    })
  })
})

// Navigation test
import { NavigationContainer } from '@react-navigation/native'
import { createNativeStackNavigator } from '@react-navigation/native-stack'

const Stack = createNativeStackNavigator()

function renderWithNavigation(component, { initialRouteName = 'Test' } = {}) {
  return render(
    <NavigationContainer>
      <Stack.Navigator initialRouteName={initialRouteName}>
        <Stack.Screen name="Test" component={component} />
        <Stack.Screen name="Detail" component={DetailScreen} />
      </Stack.Navigator>
    </NavigationContainer>
  )
}

// Custom hook test
import { renderHook, act } from '@testing-library/react-native'
import { useCounter } from './useCounter'

test('increments counter', () => {
  const { result } = renderHook(() => useCounter(0))

  act(() => {
    result.current.increment()
  })

  expect(result.current.count).toBe(1)
})

23. Hoe implementeer je E2E-tests met Detox?

Detox laat toe om de applicatie op echte simulators en emulators te testen.

jsx
// Installation
// npm install detox --save-dev
// detox init -r jest

// .detoxrc.js
module.exports = {
  testRunner: {
    args: {
      $0: 'jest',
      config: 'e2e/jest.config.js'
    },
    jest: {
      setupTimeout: 120000
    }
  },
  apps: {
    'ios.debug': {
      type: 'ios.app',
      binaryPath: 'ios/build/MyApp.app',
      build: 'xcodebuild -workspace ios/MyApp.xcworkspace -scheme MyApp -configuration Debug -sdk iphonesimulator -derivedDataPath ios/build'
    },
    'android.debug': {
      type: 'android.apk',
      binaryPath: 'android/app/build/outputs/apk/debug/app-debug.apk',
      build: 'cd android && ./gradlew assembleDebug assembleAndroidTest -DtestBuildType=debug'
    }
  },
  devices: {
    simulator: {
      type: 'ios.simulator',
      device: { type: 'iPhone 15' }
    },
    emulator: {
      type: 'android.emulator',
      device: { avdName: 'Pixel_5_API_34' }
    }
  }
}

// e2e/login.test.js
describe('Login Flow', () => {
  beforeAll(async () => {
    await device.launchApp()
  })

  beforeEach(async () => {
    await device.reloadReactNative()
  })

  it('should login successfully with valid credentials', async () => {
    // Fill the form
    await element(by.id('email-input')).typeText('test@example.com')
    await element(by.id('password-input')).typeText('password123')

    // Submit
    await element(by.id('login-button')).tap()

    // Verify navigation to dashboard
    await waitFor(element(by.text('Welcome')))
      .toBeVisible()
      .withTimeout(5000)
  })

  it('should show error with invalid credentials', async () => {
    await element(by.id('email-input')).typeText('wrong@example.com')
    await element(by.id('password-input')).typeText('wrongpassword')
    await element(by.id('login-button')).tap()

    await expect(element(by.text('Invalid credentials'))).toBeVisible()
  })

  it('should navigate to forgot password', async () => {
    await element(by.id('forgot-password-link')).tap()

    await expect(element(by.text('Reset Password'))).toBeVisible()
  })
})

// Detox commands
// detox build --configuration ios.debug
// detox test --configuration ios.debug

Deployment en productie

24. Hoe beheer je omgevingen (dev, staging, prod)?

Het beheer van omgevingen vraagt om aparte configuratievariabelen.

jsx
// Option 1: react-native-config
// .env.development
API_URL=https://dev-api.myapp.com
ANALYTICS_KEY=dev_key

// .env.staging
API_URL=https://staging-api.myapp.com
ANALYTICS_KEY=staging_key

// .env.production
API_URL=https://api.myapp.com
ANALYTICS_KEY=prod_key

// Usage
import Config from 'react-native-config'

const api = {
  baseUrl: Config.API_URL,
  analyticsKey: Config.ANALYTICS_KEY
}

// Option 2: JavaScript configuration file
// config/index.js
const ENV = {
  development: {
    apiUrl: 'https://dev-api.myapp.com',
    analyticsEnabled: false,
    logLevel: 'debug'
  },
  staging: {
    apiUrl: 'https://staging-api.myapp.com',
    analyticsEnabled: true,
    logLevel: 'info'
  },
  production: {
    apiUrl: 'https://api.myapp.com',
    analyticsEnabled: true,
    logLevel: 'error'
  }
}

const getEnv = () => {
  if (__DEV__) return 'development'
  // Logic to determine staging vs prod
  return 'production'
}

export const config = ENV[getEnv()]

// Option 3: Expo with app.config.js
// app.config.js
export default ({ config }) => {
  const env = process.env.APP_ENV || 'development'

  const envConfig = {
    development: {
      apiUrl: 'https://dev-api.myapp.com',
      bundleId: 'com.myapp.dev'
    },
    production: {
      apiUrl: 'https://api.myapp.com',
      bundleId: 'com.myapp'
    }
  }

  return {
    ...config,
    extra: {
      ...envConfig[env],
      env
    },
    ios: {
      bundleIdentifier: envConfig[env].bundleId
    },
    android: {
      package: envConfig[env].bundleId
    }
  }
}

25. Hoe deploy je naar de app stores?

Deployment omvat de build-configuratie, metadata en submission.

bash
# Option 1: EAS Build (Expo)
# Installation
npm install -g eas-cli

# Configuration
eas build:configure

# eas.json
{
  "cli": {
    "version": ">= 5.0.0"
  },
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal"
    },
    "preview": {
      "distribution": "internal",
      "android": {
        "buildType": "apk"
      }
    },
    "production": {
      "autoIncrement": true
    }
  },
  "submit": {
    "production": {
      "ios": {
        "appleId": "your@email.com",
        "ascAppId": "1234567890"
      },
      "android": {
        "serviceAccountKeyPath": "./google-services.json",
        "track": "production"
      }
    }
  }
}

# Production build
eas build --platform all --profile production

# Store submission
eas submit --platform all --profile production

# Option 2: Fastlane (React Native CLI)
# Gemfile
source "https://rubygems.org"
gem "fastlane"

# ios/fastlane/Fastfile
default_platform(:ios)

platform :ios do
  desc "Deploy to TestFlight"
  lane :beta do
    increment_build_number(xcodeproj: "MyApp.xcodeproj")
    build_app(scheme: "MyApp")
    upload_to_testflight
  end

  desc "Deploy to App Store"
  lane :release do
    increment_build_number(xcodeproj: "MyApp.xcodeproj")
    build_app(scheme: "MyApp")
    upload_to_app_store(
      skip_screenshots: true,
      skip_metadata: true
    )
  end
end

# android/fastlane/Fastfile
default_platform(:android)

platform :android do
  desc "Deploy to Play Store internal"
  lane :beta do
    gradle(task: "clean bundleRelease")
    upload_to_play_store(
      track: "internal",
      aab: "app/build/outputs/bundle/release/app-release.aab"
    )
  end
end

26. Hoe implementeer je OTA-updates?

Over-The-Air-updates maken het mogelijk om JavaScript-code uit te rollen zonder via de stores te gaan.

jsx
// With Expo Updates
import * as Updates from 'expo-updates'

async function checkForUpdates() {
  if (__DEV__) return // Not in development

  try {
    const update = await Updates.checkForUpdateAsync()

    if (update.isAvailable) {
      // Download update
      await Updates.fetchUpdateAsync()

      // Ask user to restart
      Alert.alert(
        'Update available',
        'A new version is available. Restart now?',
        [
          { text: 'Later', style: 'cancel' },
          {
            text: 'Restart',
            onPress: () => Updates.reloadAsync()
          }
        ]
      )
    }
  } catch (error) {
    console.error('Update check error:', error)
  }
}

// Automatic check on startup
function App() {
  useEffect(() => {
    checkForUpdates()
  }, [])

  return <AppNavigator />
}

// eas.json configuration for update channels
{
  "build": {
    "production": {
      "channel": "production"
    },
    "preview": {
      "channel": "preview"
    }
  }
}

// Command to publish an update
// eas update --branch production --message "Bug fix"

// With CodePush (Microsoft)
import codePush from 'react-native-code-push'

const codePushOptions = {
  checkFrequency: codePush.CheckFrequency.ON_APP_RESUME,
  installMode: codePush.InstallMode.ON_NEXT_RESTART
}

function App() {
  return <AppNavigator />
}

export default codePush(codePushOptions)(App)

Geavanceerde vragen

27. Hoe optimaliseer je de opstarttijd van de app?

De opstarttijd is bepalend voor de gebruikerservaring.

1. Enable Hermes (optimized JS engine)jsx
// android/app/build.gradle
project.ext.react = [
    enableHermes: true
]

// ios/Podfile
:hermes_enabled => true

// 2. Lazy loading screens
const HeavyScreen = React.lazy(() => import('./HeavyScreen'))

// 3. Defer non-critical initializations
import { InteractionManager } from 'react-native'

function App() {
  useEffect(() => {
    // Execute after first render
    InteractionManager.runAfterInteractions(() => {
      // Initialize analytics
      Analytics.init()
      // Prefetch data
      prefetchCriticalData()
    })
  }, [])

  return <AppNavigator />
}

// 4. Optimize splash screen
import * as SplashScreen from 'expo-splash-screen'

// Prevent automatic hiding
SplashScreen.preventAutoHideAsync()

function App() {
  const [appIsReady, setAppIsReady] = useState(false)

  useEffect(() => {
    async function prepare() {
      try {
        // Load critical resources
        await Font.loadAsync(customFonts)
        await Image.prefetch(criticalImages)
        // Restore authentication
        await restoreAuth()
      } catch (e) {
        console.warn(e)
      } finally {
        setAppIsReady(true)
      }
    }

    prepare()
  }, [])

  const onLayoutRootView = useCallback(async () => {
    if (appIsReady) {
      // Hide splash screen
      await SplashScreen.hideAsync()
    }
  }, [appIsReady])

  if (!appIsReady) return null

  return (
    <View style={{ flex: 1 }} onLayout={onLayoutRootView}>
      <AppNavigator />
    </View>
  )
}

// 5. Inline requires to defer imports
// metro.config.js
module.exports = {
  transformer: {
    inlineRequires: true
  }
}

// Manual usage
function loadHeavyModule() {
  const HeavyModule = require('./HeavyModule').default
  return HeavyModule
}

28. Hoe ga je om met security in een React Native-app?

Mobiele beveiliging vraagt om meerdere beschermingslagen.

1. Secure storage for sensitive datajsx
import * as SecureStore from 'expo-secure-store'
// or
import * as Keychain from 'react-native-keychain'

async function saveToken(token) {
  await SecureStore.setItemAsync('auth_token', token)
}

async function getToken() {
  return await SecureStore.getItemAsync('auth_token')
}

// 2. Certificate pinning for network calls
// android/app/src/main/res/xml/network_security_config.xml
/*
<network-security-config>
  <domain-config>
    <domain includeSubdomains="true">api.myapp.com</domain>
    <pin-set>
      <pin digest="SHA-256">AAAAAA...</pin>
      <pin digest="SHA-256">BBBBBB...</pin>
    </pin-set>
  </domain-config>
</network-security-config>
*/

// 3. Jailbreak/root detection
import JailMonkey from 'jail-monkey'

function SecurityCheck() {
  useEffect(() => {
    if (JailMonkey.isJailBroken()) {
      Alert.alert(
        'Insecure device',
        'This application cannot run on a rooted/jailbroken device'
      )
    }
  }, [])
}

// 4. Code obfuscation
// metro.config.js (for Hermes)
module.exports = {
  transformer: {
    minifierConfig: {
      mangle: true,
      output: {
        ascii_only: true
      }
    }
  }
}

// 5. Screenshot/recording protection
import { usePreventScreenCapture } from 'expo-screen-capture'

function SensitiveScreen() {
  usePreventScreenCapture() // iOS only

  return <View>{/* Sensitive data */}</View>
}

// 6. Session timeout
function useSessionTimeout(timeoutMs = 5 * 60 * 1000) {
  const lastActivity = useRef(Date.now())
  const { logout } = useAuth()

  useEffect(() => {
    const subscription = AppState.addEventListener('change', (state) => {
      if (state === 'active') {
        const elapsed = Date.now() - lastActivity.current
        if (elapsed > timeoutMs) {
          logout()
        }
      } else {
        lastActivity.current = Date.now()
      }
    })

    return () => subscription.remove()
  }, [timeoutMs, logout])
}

29. Hoe implementeer je toegankelijkheid?

Toegankelijkheid is essentieel om de app voor iedereen bruikbaar te maken.

jsx
import { AccessibilityInfo } from 'react-native'

// 1. Basic accessibility props
function AccessibleButton({ label, onPress, disabled }) {
  return (
    <TouchableOpacity
      onPress={onPress}
      disabled={disabled}
      accessible={true}
      accessibilityLabel={label}
      accessibilityRole="button"
      accessibilityState={{ disabled }}
      accessibilityHint={`Tap to ${label.toLowerCase()}`}
    >
      <Text>{label}</Text>
    </TouchableOpacity>
  )
}

// 2. Group elements for screen readers
function ProductCard({ product }) {
  return (
    <View
      accessible={true}
      accessibilityLabel={`${product.name}, ${product.price} dollars`}
    >
      <Image
        source={{ uri: product.image }}
        accessibilityIgnoresInvertColors={true}
      />
      <Text>{product.name}</Text>
      <Text>${product.price}</Text>
    </View>
  )
}

// 3. Announce dynamic changes
function NotificationBadge({ count }) {
  useEffect(() => {
    if (count > 0) {
      AccessibilityInfo.announceForAccessibility(
        `${count} new notification${count > 1 ? 's' : ''}`
      )
    }
  }, [count])

  return (
    <View accessibilityLabel={`${count} notifications`}>
      <Text>{count}</Text>
    </View>
  )
}

// 4. Detect accessibility preferences
function useAccessibilityPreferences() {
  const [isScreenReaderEnabled, setIsScreenReaderEnabled] = useState(false)
  const [isReduceMotionEnabled, setIsReduceMotionEnabled] = useState(false)

  useEffect(() => {
    AccessibilityInfo.isScreenReaderEnabled().then(setIsScreenReaderEnabled)
    AccessibilityInfo.isReduceMotionEnabled().then(setIsReduceMotionEnabled)

    const screenReaderListener = AccessibilityInfo.addEventListener(
      'screenReaderChanged',
      setIsScreenReaderEnabled
    )
    const reduceMotionListener = AccessibilityInfo.addEventListener(
      'reduceMotionChanged',
      setIsReduceMotionEnabled
    )

    return () => {
      screenReaderListener.remove()
      reduceMotionListener.remove()
    }
  }, [])

  return { isScreenReaderEnabled, isReduceMotionEnabled }
}

// 5. Adapt animations based on preferences
function AnimatedComponent() {
  const { isReduceMotionEnabled } = useAccessibilityPreferences()

  const animation = useSharedValue(0)

  useEffect(() => {
    animation.value = withTiming(1, {
      duration: isReduceMotionEnabled ? 0 : 300
    })
  }, [isReduceMotionEnabled])

  return <Animated.View style={animatedStyle} />
}

30. Hoe structureer je een groot React Native-project?

Een heldere architectuur vergemakkelijkt onderhoud en schaalbaarheid.

text
// Recommended structure
src/
├── app/                    # App configuration
│   ├── App.tsx
│   ├── Navigation.tsx
│   └── Providers.tsx
├── features/               # Feature modules
│   ├── auth/
│   │   ├── screens/
│   │   │   ├── LoginScreen.tsx
│   │   │   └── RegisterScreen.tsx
│   │   ├── components/
│   │   │   └── AuthForm.tsx
│   │   ├── hooks/
│   │   │   └── useAuth.ts
│   │   ├── services/
│   │   │   └── authService.ts
│   │   └── index.ts        # Public export
│   │
│   ├── products/
│   │   ├── screens/
│   │   ├── components/
│   │   ├── hooks/
│   │   └── services/
│   │
│   └── cart/
│       └── ...
├── shared/                 # Shared code
│   ├── components/
│   │   ├── Button.tsx
│   │   ├── Input.tsx
│   │   └── Card.tsx
│   ├── hooks/
│   │   ├── useDebounce.ts
│   │   └── useNetworkStatus.ts
│   ├── utils/
│   │   ├── format.ts
│   │   └── validation.ts
│   └── types/
│       └── index.ts
├── services/               # Global services
│   ├── api/
│   │   ├── client.ts
│   │   └── interceptors.ts
│   ├── storage/
│   │   └── secureStorage.ts
│   └── analytics/
│       └── analytics.ts
├── store/                  # Global state
│   ├── slices/
│   └── index.ts
└── theme/                  # Design system
    ├── colors.ts
    ├── typography.ts
    ├── spacing.ts
    └── index.ts
jsx
// Example feature module organization
// features/products/index.ts
export { ProductListScreen } from './screens/ProductListScreen'
export { ProductDetailScreen } from './screens/ProductDetailScreen'
export { useProducts } from './hooks/useProducts'
export { ProductCard } from './components/ProductCard'

// features/products/hooks/useProducts.ts
import { useQuery } from '@tanstack/react-query'
import { productService } from '../services/productService'

export function useProducts(categoryId?: string) {
  return useQuery({
    queryKey: ['products', categoryId],
    queryFn: () => productService.getProducts(categoryId)
  })
}

// features/products/services/productService.ts
import { apiClient } from '@/services/api/client'
import { Product } from '../types'

export const productService = {
  async getProducts(categoryId?: string): Promise<Product[]> {
    const params = categoryId ? { category: categoryId } : {}
    const response = await apiClient.get('/products', { params })
    return response.data
  },

  async getProduct(id: string): Promise<Product> {
    const response = await apiClient.get(`/products/${id}`)
    return response.data
  }
}

// Import alias configuration
// babel.config.js
module.exports = {
  presets: ['module:@react-native/babel-preset'],
  plugins: [
    [
      'module-resolver',
      {
        alias: {
          '@': './src',
          '@features': './src/features',
          '@shared': './src/shared',
          '@services': './src/services'
        }
      }
    ]
  ]
}

Conclusie

Deze 30 vragen dekken de essentiële React Native-kennis die in sollicitaties wordt verwacht. Belangrijke onderwerpen om te beheersen:

  • Architectuur: bridge, JSI en de nieuwe architectuur begrijpen
  • Componenten: navigatie, performante lijsten, animaties
  • State en data: Zustand/Redux, React Query, lokale opslag
  • Performance: FlatList-optimalisatie, memoisatie, profiling
  • Mobiele specificiteiten: permissies, notificaties, deep links
  • Testen: Jest, Testing Library, Detox
  • Deployment: EAS Build, stores, OTA-updates
  • Security en toegankelijkheid: secure storage, WCAG-conformiteit

De voorbereiding op een React Native-sollicitatie vereist begrip van mobiele aspecten die verder gaan dan kennis van React op het web. Oefenen op echte projecten en testen op fysieke toestellen verankert deze concepten.

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