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 — Expo Router: Stack, Tabs, NativeTabs (headerLargeTitle, headerBackButtonDisplayMode), links, modals, sheets, context menus
• references/components.md — FlashList patterns, expo-image, safe areas (contentInsetAdjustmentBehavior), native controls, blur/glass effects, storage
• references/styling.md — StyleSheet, NativeWind/Tailwind, platform styles, theming, dark mode
• references/animations.md — Reanimated 3: entering/exiting, shared values, gestures, scroll-driven
• references/state-management.md — Zustand (selectors, persist), Jotai (atoms, derived), React Query, Context
• references/forms.md — React Hook Form + Zod: validation, multi-step, dynamic arrays
• references/networking.md — fetch wrapper, React Query (optimistic updates), auth tokens, offline, API routes, webhooks
• references/performance.md — Profiling workflow, FlashList + memo, bundle analysis, TTI, memory leaks, animation perf
• references/testing.md — Jest, React Native Testing Library, E2E with Maestro
• references/native-capabilities.md — Camera, location, permissions (use*Permissions hooks), haptics, notifications, biometrics
• 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

# 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)

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

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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.