MAJOR.MINOR.PATCH (e.g., 2.3.1)

MAJOR: Breaking changes
MINOR: New features, backward compatible
PATCH: Bug fixes, backward compatible

^2.3.1 = >=2.3.1 <3.0.0 (minor updates)
~2.3.1 = >=2.3.1 <2.4.0 (patch updates)
2.3.1 = exact version

# npm
npm outdated
npm audit
npm audit fix

# yarn
yarn outdated
yarn audit

# Check for major updates
npx npm-check-updates
npx npm-check-updates -u  # Update package.json

# See why a package is installed
npm ls package-name
yarn why package-name

# Find duplicate packages
npm dedupe
yarn dedupe

# Visualize dependencies
npx madge --image graph.png src/

// compatibility-matrix.js
const compatibilityMatrix = {
  'react': {
    '16.x': {
      'react-dom': '^16.0.0',
      'react-router-dom': '^5.0.0',
      '@testing-library/react': '^11.0.0'
    },
    '17.x': {
      'react-dom': '^17.0.0',
      'react-router-dom': '^5.0.0 || ^6.0.0',
      '@testing-library/react': '^12.0.0'
    },
    '18.x': {
      'react-dom': '^18.0.0',
      'react-router-dom': '^6.0.0',
      '@testing-library/react': '^13.0.0'
    }
  }
};

function checkCompatibility(packages) {
  // Validate package versions against matrix
}

# 1. Identify current versions
npm list --depth=0

# 2. Check for breaking changes
# Read CHANGELOG.md and MIGRATION.md

# 3. Create upgrade plan
echo "Upgrade order:
1. TypeScript
2. React
3. React Router
4. Testing libraries
5. Build tools" > UPGRADE_PLAN.md

# Don't upgrade everything at once!

# Step 1: Update TypeScript
npm install typescript@latest

# Test
npm run test
npm run build

# Step 2: Update React (one major version at a time)
npm install react@17 react-dom@17

# Test again
npm run test

# Step 3: Continue with other packages
npm install react-router-dom@6

# And so on...

// tests/compatibility.test.js
describe('Dependency Compatibility', () => {
  it('should have compatible React versions', () => {
    const reactVersion = require('react/package.json').version;
    const reactDomVersion = require('react-dom/package.json').version;

    expect(reactVersion).toBe(reactDomVersion);
  });

  it('should not have peer dependency warnings', () => {
    // Run npm ls and check for warnings
  });
});

# Use changelog parsers
npx changelog-parser react 16.0.0 17.0.0

# Or manually check
curl https://raw.githubusercontent.com/facebook/react/main/CHANGELOG.md

# React upgrade codemods
npx react-codeshift <transform> <path>

# Example: Update lifecycle methods
npx react-codeshift \
  --parser tsx \
  --transform react-codeshift/transforms/rename-unsafe-lifecycles.js \
  src/

// migration-script.js
const fs = require('fs');
const glob = require('glob');

glob('src/**/*.tsx', (err, files) => {
  files.forEach(file => {
    let content = fs.readFileSync(file, 'utf8');

    // Replace old API with new API
    content = content.replace(
      /componentWillMount/g,
      'UNSAFE_componentWillMount'
    );

    // Update imports
    content = content.replace(
      /import { Component } from 'react'/g,
      "import React, { Component } from 'react'"
    );

    fs.writeFileSync(file, content);
  });
});

// Ensure tests pass before and after upgrade
npm run test

// Update test utilities if needed
npm install @testing-library/react@latest

// tests/integration/app.test.js
describe('App Integration', () => {
  it('should render without crashing', () => {
    render(<App />);
  });

  it('should handle navigation', () => {
    const { getByText } = render(<App />);
    fireEvent.click(getByText('Navigate'));
    expect(screen.getByText('New Page')).toBeInTheDocument();
  });
});