What are the common development tools and debugging techniques in Expo?

Expo provides rich development tools and debugging features to help developers improve development efficiency and code quality. Mastering these tools is crucial for Expo development.

Core Development Tools:

1. Expo CLI

Expo CLI is the main command-line tool, providing project creation, development server startup, build, and other functions.

Common Commands:

bash
# Create new project
npx create-expo-app my-app

# Start development server
npx expo start

# Clear cache
npx expo start -c

# View device info
npx expo start --tunnel

# Generate app icon
npx expo install expo-app-icon

1. Expo Dev Tools

Expo Dev Tools is a web-based development tool interface providing visual project management features.

Features:

• Device connection management
• Log viewing
• Performance monitoring
• Fast refresh control
• Network request monitoring

1. React Native Debugger

React Native Debugger is a standalone debugging tool that integrates React DevTools and Redux DevTools.

Usage:

bash
# Install
npm install -g react-native-debugger

# Start
react-native-debugger

Debugging Techniques:

1. Console Debugging

Use console.log to output debug information:

typescript
console.log('Debug info');
console.warn('Warning message');
console.error('Error message');

// Use console.group to organize logs
console.group('User Data');
console.log('Name:', user.name);
console.log('Age:', user.age);
console.groupEnd();

1. React DevTools

React DevTools provides component tree viewing, props inspection, state monitoring, and other features.

Usage:

typescript
// Enable in development environment
if (__DEV__) {
  const DevTools = require('react-devtools');
  DevTools.connectToDevTools({
    host: 'localhost',
    port: 8097,
  });
}

1. Flipper

Flipper is a mobile app debugging tool developed by Facebook, supporting network requests, database, layout inspection, etc.

Configure Flipper:

javascript
// In metro.config.js
const { getDefaultConfig } = require('expo/metro-config');

const config = getDefaultConfig(__dirname);

module.exports = config;

1. Reactotron

Reactotron is a powerful debugging tool supporting Redux, API calls, logs, and other features.

Configure Reactotron:

typescript
import Reactotron from 'reactotron-react-native';

if (__DEV__) {
  const tron = Reactotron
    .configure()
    .useReactNative()
    .connect();

  console.tron = tron;
}

Performance Optimization Tools:

1. Performance Monitoring

Use React Native Performance API:

typescript
import { Performance } from 'react-native';

// Record performance mark
Performance.mark('component-start');

// After component renders
Performance.mark('component-end');

// Measure performance
Performance.measure('component-render', 'component-start', 'component-end');

1. Memory Analysis

Use Flipper or React Native Debugger to view memory usage:

• Monitor memory leaks
• Analyze component rendering performance
• Optimize image and resource loading

1. Bundle Analysis

Use webpack-bundle-analyzer to analyze bundle size:

bash
npm install --save-dev @expo/webpack-config webpack-bundle-analyzer

Error Handling:

1. Error Boundaries

Use React error boundaries to catch component errors:

typescript
class ErrorBoundary extends React.Component {
  state = { hasError: false };

  static getDerivedStateFromError(error) {
    return { hasError: true };
  }

  componentDidCatch(error, errorInfo) {
    console.error('Error caught by boundary:', error, errorInfo);
  }

  render() {
    if (this.state.hasError) {
      return <Text>Something went wrong.</Text>;
    }
    return this.props.children;
  }
}

1. Global Error Handling

Listen to global error events:

typescript
// JavaScript errors
const defaultErrorHandler = ErrorUtils.getGlobalHandler();
ErrorUtils.setGlobalHandler((error, isFatal) => {
  console.error('Global error:', error);
  defaultErrorHandler(error, isFatal);
});

// Promise errors
process.on('unhandledRejection', (error) => {
  console.error('Unhandled promise rejection:', error);
});

Testing Tools:

1. Jest

Jest is Expo's default testing framework:

typescript
// Example test
import { render } from '@testing-library/react-native';
import MyComponent from './MyComponent';

test('renders correctly', () => {
  const { getByText } = render(<MyComponent />);
  expect(getByText('Hello')).toBeTruthy();
});

1. Detox

Detox is an end-to-end testing framework:

typescript
describe('Login Flow', () => {
  it('should login successfully', async () => {
    await element(by.id('username')).typeText('user@example.com');
    await element(by.id('password')).typeText('password');
    await element(by.id('login-button')).tap();
    await expect(element(by.id('welcome'))).toBeVisible();
  });
});

Best Practices:

1. Development Environment Configuration: Use different environment variables for development, testing, and production environments

2. Log Management: Disable detailed log output in production environment

3. Error Tracking: Integrate error tracking services like Sentry or Bugsnag

4. Performance Monitoring: Regularly monitor app performance metrics

5. Automated Testing: Establish a comprehensive testing system

Mastering these debugging tools and techniques can greatly improve Expo development efficiency and quality.