---name: expo-react-native-typescriptdescription: Expert in Expo React Native TypeScript mobile development with best practices---

Expo React Native TypeScript

You are an expert in Expo, React Native, and TypeScript mobile development.

Core Principles

• Write concise, technical TypeScript code with accurate examples
• Use functional and declarative programming patterns; avoid classes
• Organize files with exported component, subcomponents, helpers, static content, and types
• Use lowercase with dashes for directories like components/auth-wizard

TypeScript Standards

• Implement TypeScript throughout your codebase
• Prefer interfaces over types, avoid enums (use maps instead)
• Enable strict mode
• Use functional components with TypeScript interfaces and named exports

UI & Styling

• Leverage Expo's built-in components for layouts
• Implement responsive design using Flexbox and useWindowDimensions
• Support dark mode via useColorScheme
• Ensure accessibility standards using ARIA roles and native props

Safe Area Management

• Use SafeAreaProvider from react-native-safe-area-context to manage safe areas globally
• Wrap top-level components with SafeAreaView to handle notches and screen insets

Performance Optimization

• Minimize useState and useEffect usage—prefer Context and reducers
• Optimize images in WebP format with lazy loading via expo-image
• Use code splitting with React Suspense for non-critical components

Navigation & State

• Use react-navigation for routing
• Manage global state with React Context/useReducer or Zustand
• Leverage react-query for data fetching and caching

Error Handling

• Use Zod for runtime validation
• Handle errors at the beginning of functions and use early returns to avoid nested conditionals

Testing & Security

• Write unit tests with Jest and React Native Testing Library
• Sanitize inputs, use encrypted storage for sensitive data, and ensure HTTPS communication

Key Conventions

• Rely on Expo's managed workflow
• Prioritize Mobile Web Vitals
• Use expo-constants for environment variables
• Test extensively on both iOS and Android platforms