react-native-dev

# React Native & Expo Development Guide A practical guide for building production-ready React Native and Expo applications. Covers UI, animations, state, testing, performance, and deployment. ## References Consult these resources as needed: - [references/navigation.md](references/navigation.md) — Expo Router: Stack, Tabs, NativeTabs (`headerLargeTitle`, `headerBackButtonDisplayMode`), links, modals, sheets, context menus - [references/components.md](references/components.md) — FlashList patterns, `expo-image`, safe areas (`contentInsetAdjustmentBehavior`), native controls, blur/glass effects, storage - [references/styling.md](references/styling.md) — StyleSheet, NativeWind/Tailwind, platform styles, theming, dark mode - [references/animations.md](references/animations.md) — Reanimated 3: entering/exiting, shared values, gestures, scroll-driven - [references/state-management.md](references/state-management.md) — Zustand (selectors, persist), Jotai (atoms, derived), React Query, Context - [references/forms.md](references/forms.md) — React Hook Form + Zod: validation, multi-step, dynamic arrays - [references/networking.md](references/networking.md) — fetch wrapper, React Query (optimistic updates), auth tokens, offline, API routes, webhooks - [references/performance.md](references/performance.md) — Profiling workflow, FlashList + `memo`, bundle analysis, TTI, memory leaks, animation perf - [references/testing.md](references/testing.md) — Jest, React Native Testing Library, E2E with Maestro - [references/native-capabilities.md](references/native-capabilities.md) — Camera, location, permissions (`use*Permissions` hooks), haptics, notifications, biometrics - [references/engineering.md](references/engineering.md) — Project layout (`components/ui/`, `stores/`, `services/`), path aliases, SDK upgrades, EAS build/submit, CI/CD, DOM components ## Quick Reference ### Component Preferences | Purpose | Use | Instead of | |---------|-----|------------| | Lists | `FlashList` (`@shopify/flash-list`) + `memo` items | `FlatList` (no view recycling) | | Images | `expo-image` | RN `<Image>` (no cache, no WebP) | | Press | `Pressable` | `TouchableOpacity` (legacy) | | Audio | `expo-audio` | `expo-av` (deprecated) | | Video | `expo-video` | `expo-av` (deprecated) | | Animations | Reanimated 3 | RN Animated API (limited) | | Gestures | Gesture Handler | PanResponder (legacy) | | Platform check | `process.env.EXPO_OS` | `Platform.OS` | | Context | `React.use()` | `React.useContext()` (React 18) | | Safe area scroll | `contentInsetAdjustmentBehavior="automatic"` | `<SafeAreaView>` | | SF Symbols | `expo-image` with `source="sf:name"` | `expo-symbols` | ### Scaling Up | Situation | Consider | |-----------|----------| | Long lists with scroll jank | Virtualized list libraries (e.g. FlashList) | | Want Tailwind-style classes | NativeWind v4 | | High-frequency storage reads | Sync-based storage (e.g. MMKV) | | New project with Expo | Expo Router over bare React Navigation | ### State Management | State Type | Solution | |------------|----------| | Local UI state | `useState` / `useReducer` | | Shared app state | Zustand or Jotai | | Server / async data | React Query | | Form state | React Hook Form + Zod | ### Performance Priorities | Priority | Issue | Fix | |----------|-------|-----| | CRITICAL | Long list jank | `FlashList` + memoized items | | CRITICAL | Large bundle | Avoid barrel imports, enable R8 | | HIGH | Too many re-renders | Zustand selectors, React Compiler | | HIGH | Slow startup | Disable bundle compression, native nav | | MEDIUM | Animation drops | Only animate `transform`/`opacity` | ## New Project Init ```bash # 1. Create project npx create-expo-app@latest my-app --template blank-typescript cd my-app # 2. Install Expo Router + core deps npx expo install expo-router react-native-safe-area-context react-native-screens # 3. (Optional) Common extras npx expo install expo-image react-native-reanimated react-native-gesture-handler ``` Then configure: 1. Set entry point in `package.json`: `"main": "expo-router/entry"` 2. Add scheme in `app.json`: `"scheme": "my-app"` 3. Delete `App.tsx` and `index.ts` 4. Create `app/_layout.tsx` as root Stack layout 5. Create `app/(tabs)/_layout.tsx` for tab navigation 6. Create route files in `app/(tabs)/` (see [navigation.md](references/navigation.md)) For web support, also install: `npx expo install react-native-web react-dom @expo/metro-runtime` ## Core Principles **Consult references before writing**: when implementing navigation, lists, networking, or project setup, read the matching reference file above for patterns and pitfalls. **Try Expo Go first** (`npx expo start`). Custom builds (`eas build`) only needed when using local Expo modules, Apple targets, or third-party native modules not in Expo Go. **Conditional rendering**: use `{count > 0 && <Text />}` not `{count && <Text />}` (renders "0"). **Animation rule**: only animate `transform` and `opacity` — GPU-composited, no layout thrash. **Imports**: always import directly from source, not barrel files — avoids bundle bloat. **Lists and images**: before using `FlatList` or RN `Image`, check the Component Preferences table above — `FlashList` and `expo-image` are almost always the right choice. **Route files**: always use kebab-case, never co-locate components/types/utils in `app/`. ## Checklist ### New Project Setup - [ ] `tsconfig.json` path aliases configured - [ ] `EXPO_PUBLIC_API_URL` env var set per environment - [ ] Root layout has `GestureHandlerRootView` (if using gestures) - [ ] `contentInsetAdjustmentBehavior="automatic"` on all scroll views - [ ] `FlashList` instead of `FlatList` for lists > 20 items ### Before Shipping - [ ] Profile in `--profile` mode, fix frames > 16ms - [ ] Bundle analyzed (`source-map-explorer`), no barrel imports - [ ] R8 enabled for Android - [ ] Unit + component tests for critical paths - [ ] E2E flows for login, core feature, checkout --- Flutter development → see `flutter-dev` skill. iOS native (UIKit/SwiftUI) → see `ios-application-dev` skill. Android native (Kotlin/Compose) → see `android-native-dev` skill. *React Native is a trademark of Meta Platforms, Inc. Expo is a trademark of 650 Industries, Inc. All other product names are trademarks of their respective owners.*