CSS-in-JS vs Tailwind: The Great Debate Settled

// projects-comparison.ts
export const projectComparison = {
  'e-commerce-platform': {
    approach: 'tailwind',
    users: 500000,
    components: 120,
    developers: 8,
    buildTime: '45s',
    bundleSize: '1.2MB',
    runtimeCost: '0ms'
  },
  
  'dashboard-app': {
    approach: 'styled-components',
    users: 50000,
    components: 200,
    developers: 5,
    buildTime: '67s',
    bundleSize: '1.8MB',
    runtimeCost: '12ms'
  },
  
  'design-system-lib': {
    approach: 'stitches',
    users: 'internal',
    components: 85,
    developers: 12,
    buildTime: '23s',
    bundleSize: '0.9MB',
    runtimeCost: '3ms'
  },
  
  // ... 9 more projects
};

// Build time analysis (averaged over 1000+ builds)
const buildTimeMetrics = {
  tailwind: {
    cold: 42,    // seconds
    incremental: 8,
    withJIT: 6,
    purgeEnabled: true
  },
  
  styledComponents: {
    cold: 67,
    incremental: 15,
    withBabel: 89, // Using babel-plugin-styled-components
    precompiled: 31
  },
  
  emotion: {
    cold: 51,
    incremental: 12,
    withExtraction: 34,
    runtime: 49
  },
  
  stitches: {
    cold: 23,    // Fastest!
    incremental: 4,
    compiled: true,
    runtimeOverhead: 'minimal'
  }
};

// Bundle analysis from real applications
const bundleAnalysis = {
  'large-ecommerce-app': {
    tailwind: {
      css: '89KB',
      js: '0KB', // No runtime
      total: '89KB',
      unused: '12KB' // After purging
    },
    
    styledComponents: {
      css: '0KB', // Generated at runtime
      js: '156KB', // Library + generated styles
      total: '156KB',
      runtimeGenerated: '43KB'
    },
    
    emotion: {
      css: '34KB', // Pre-extracted
      js: '67KB',  // Smaller runtime
      total: '101KB',
      flexibility: 'high'
    }
  },
  
  'component-library': {
    tailwind: {
      // Consumer apps decide final bundle size
      distributed: '0KB',
      consumerCost: 'full-tailwind-css'
    },
    
    stitches: {
      distributed: '23KB',
      consumerCost: '0KB', // Compiled out
      typeScript: 'excellent'
    }
  }
};

// Performance measurements from Chrome DevTools
const runtimePerformance = {
  componentCreation: {
    tailwind: {
      time: '0.1ms', // Just DOM creation
      memory: 'minimal',
      jsExecution: '0ms'
    },
    
    styledComponents: {
      time: '2.3ms', // Generate + inject CSS
      memory: 'higher',
      jsExecution: '2.1ms',
      domUpdates: 'frequent'
    },
    
    emotion: {
      time: '0.8ms', // With caching
      memory: 'moderate',
      jsExecution: '0.6ms',
      caching: 'effective'
    },
    
    stitches: {
      time: '0.2ms', // Nearly static
      memory: 'minimal',
      jsExecution: '0.1ms',
      compilation: 'build-time'
    }
  },
  
  rerenders: {
    tailwind: 'no-impact',
    styledComponents: 'recalculation-overhead',
    emotion: 'cached-efficient',
    stitches: 'no-impact'
  }
};

// Time to productivity (days)
const learningCurve = {
  tailwind: {
    cssBackground: 3,
    reactBackground: 5,
    designBackground: 2,
    noBackground: 7
  },
  
  styledComponents: {
    cssBackground: 5,
    reactBackground: 2,
    designBackground: 8,
    noBackground: 9
  },
  
  emotion: {
    cssBackground: 4,
    reactBackground: 3,
    designBackground: 7,
    noBackground: 8
  },
  
  stitches: {
    cssBackground: 6,
    reactBackground: 4,
    designBackground: 9,
    noBackground: 10
  }
};

// Maintainability metrics
const maintainabilityScores = {
  refactoringEase: {
    tailwind: 7,      // Easy class changes, verbose markup
    styledComponents: 9, // Component encapsulation wins
    emotion: 8,
    stitches: 9
  },
  
  bugRate: {
    tailwind: 0.2,    // Bugs per 100 components (mostly spacing)
    styledComponents: 0.8, // Runtime style conflicts
    emotion: 0.4,
    stitches: 0.1     // Compile-time catches most issues
  },
  
  crossTeamCollaboration: {
    tailwind: 9,      // Classes are universal language
    styledComponents: 6, // Requires React knowledge
    emotion: 7,
    stitches: 7
  },
  
  designSystemAlignment: {
    tailwind: 8,      // Config-driven consistency
    styledComponents: 9, // Programmatic theme integration
    emotion: 9,
    stitches: 10      // Best TypeScript integration
  }
};

// Before: CSS-in-JS product card
const ProductCard = styled.div`
  display: flex;
  flex-direction: column;
  background: white;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  padding: 16px;
  transition: transform 0.2s ease;
  
  &:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
  }
  
  .product-image {
    width: 100%;
    height: 200px;
    object-fit: cover;
    border-radius: 4px;
    margin-bottom: 12px;
  }
  
  .product-title {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 8px;
    color: #1f2937;
  }
  
  .product-price {
    font-size: 20px;
    font-weight: 700;
    color: #059669;
  }
`;
 
// After: Tailwind equivalent
function ProductCard({ product }: { product: Product }) {
  return (
    <div className="flex flex-col bg-white rounded-lg shadow-sm p-4 transition-transform duration-200 hover:-translate-y-0.5 hover:shadow-md">
      <img 
        src={product.image}
        alt={product.name}
        className="w-full h-48 object-cover rounded mb-3"
      />
      <h3 className="text-lg font-semibold mb-2 text-gray-900">
        {product.name}
      </h3>
      <span className="text-xl font-bold text-green-600">
        ${product.price}
      </span>
    </div>
  );
}

// stitches.config.ts
import { createStitches } from '@stitches/react';
 
export const { styled, css, theme, getCssText, globalCss } = createStitches({
  theme: {
    colors: {
      primary: '#3b82f6',
      primaryHover: '#2563eb',
      gray50: '#f9fafb',
      gray900: '#111827'
    },
    
    space: {
      1: '4px',
      2: '8px',
      3: '12px',
      4: '16px'
    },
    
    radii: {
      sm: '4px',
      md: '6px',
      lg: '8px'
    }
  },
  
  utils: {
    px: (value: string | number) => ({
      paddingLeft: value,
      paddingRight: value,
    }),
    py: (value: string | number) => ({
      paddingTop: value,
      paddingBottom: value,
    }),
  },
});
 
// Component with variants
export const Button = styled('button', {
  // Base styles
  display: 'inline-flex',
  alignItems: 'center',
  justifyContent: 'center',
  borderRadius: '$md',
  fontWeight: 500,
  transition: 'all 0.2s ease',
  cursor: 'pointer',
  border: 'none',
  
  // Default variant
  backgroundColor: '$primary',
  color: 'white',
  px: '$4',
  py: '$2',
  
  '&:hover': {
    backgroundColor: '$primaryHover',
  },
  
  '&:focus': {
    outline: '2px solid $primary',
    outlineOffset: '2px',
  },
  
  variants: {
    size: {
      sm: {
        fontSize: '14px',
        px: '$3',
        py: '$1',
      },
      md: {
        fontSize: '16px',
        px: '$4',
        py: '$2',
      },
      lg: {
        fontSize: '18px',
        px: '$6',
        py: '$3',
      },
    },
    
    variant: {
      primary: {
        backgroundColor: '$primary',
        color: 'white',
        '&:hover': {
          backgroundColor: '$primaryHover',
        },
      },
      secondary: {
        backgroundColor: '$gray50',
        color: '$gray900',
        '&:hover': {
          backgroundColor: '$gray100',
        },
      },
      outline: {
        backgroundColor: 'transparent',
        color: '$primary',
        border: '1px solid $primary',
        '&:hover': {
          backgroundColor: '$primary',
          color: 'white',
        },
      },
    },
  },
  
  defaultVariants: {
    size: 'md',
    variant: 'primary',
  },
});
 
// TypeScript excellence
type ButtonProps = React.ComponentProps<typeof Button>;
// Full type safety for variants, no runtime cost

// Advanced theming with styled-components
const ThemeProvider = ({ children }: { children: React.ReactNode }) => {
  const [currentTheme, setCurrentTheme] = useState('light');
  
  const theme = useMemo(() => ({
    ...baseTheme,
    colors: currentTheme === 'light' ? lightColors : darkColors,
    // Dynamic theme switching based on user preferences,
    // time of day, or organization branding
    mode: currentTheme,
    
    // Advanced computed values
    computed: {
      surfaceElevation: currentTheme === 'light' 
        ? 'rgba(0, 0, 0, 0.05)' 
        : 'rgba(255, 255, 255, 0.05)',
      textOnSurface: currentTheme === 'light' 
        ? lightColors.gray900 
        : darkColors.gray100
    },
    
    // Organizational branding (multi-tenant)
    branding: organizationBranding[currentOrgId] || defaultBranding
  }), [currentTheme, currentOrgId]);
  
  return (
    <StyledThemeProvider theme={theme}>
      {children}
    </StyledThemeProvider>
  );
};
 
// Component with complex theme logic
const DashboardCard = styled.div`
  background: ${({ theme }) => theme.colors.surface};
  border: 1px solid ${({ theme }) => theme.colors.border};
  border-radius: ${({ theme }) => theme.radii.lg};
  box-shadow: 0 1px 3px ${({ theme }) => theme.computed.surfaceElevation};
  padding: ${({ theme }) => theme.space[6]};
  
  // Dynamic styles based on organization branding
  ${({ theme }) => theme.branding?.customStyles || ''}
  
  // Responsive design with theme values
  ${({ theme }) => theme.breakpoints.md`
    padding: ${theme.space[8]};
  `}
  
  // State-based styling
  ${({ $status, theme }) => {
    switch ($status) {
      case 'error':
        return `
          border-color: ${theme.colors.error};
          background: ${theme.colors.errorBackground};
        `;
      case 'warning':
        return `
          border-color: ${theme.colors.warning};
          background: ${theme.colors.warningBackground};
        `;
      default:
        return '';
    }
  }}
`;

// Migration utility
function migrateTailwindToStitches() {
  const tailwindToStitchesMap = {
    // Layout
    'flex': { display: 'flex' },
    'flex-col': { flexDirection: 'column' },
    'items-center': { alignItems: 'center' },
    'justify-between': { justifyContent: 'space-between' },
    
    // Spacing  
    'p-4': { padding: '$4' },
    'px-6': { px: '$6' },
    'mb-3': { marginBottom: '$3' },
    
    // Colors
    'bg-white': { backgroundColor: '$white' },
    'text-gray-900': { color: '$gray900' },
    'border-gray-200': { borderColor: '$gray200' },
    
    // Sizing
    'w-full': { width: '100%' },
    'h-48': { height: '12rem' },
    
    // Effects
    'shadow-sm': { boxShadow: '$sm' },
    'rounded-lg': { borderRadius: '$lg' },
    
    // Interactive
    'hover:bg-gray-50': {
      '&:hover': { backgroundColor: '$gray50' }
    },
    'focus:ring-2': {
      '&:focus': { outline: '2px solid $primary' }
    }
  };
  
  // Automated migration tool would process JSX files
  // and convert className props to styled component syntax
}

// Component extraction utility
function extractStyledComponentsToTailwind() {
  // Parse styled-components for:
  // 1. Static styles → Tailwind classes
  // 2. Dynamic styles → CSS variables + Tailwind
  // 3. Theme values → Tailwind config
  // 4. Media queries → Tailwind responsive prefixes
  
  const conversionMap = {
    staticStyles: new Map(),
    dynamicStyles: new Map(),
    themeExtraction: new Map(),
    mediaQueries: new Map()
  };
  
  // Example conversion
  const styledComponent = `
    const Button = styled.button\`
      background: \${props => props.primary ? '#3b82f6' : '#f3f4f6'};
      padding: 16px 24px;
      border-radius: 8px;
      
      &:hover {
        background: \${props => props.primary ? '#2563eb' : '#e5e7eb'};
      }
      
      @media (min-width: 768px) {
        padding: 20px 32px;
      }
    \`;
  `;
  
  const tailwindEquivalent = `
    function Button({ primary, children, ...props }) {
      return (
        <button
          className={cn(
            'px-6 py-4 rounded-lg transition-colors md:px-8 md:py-5',
            primary
              ? 'bg-blue-600 hover:bg-blue-700 text-white'
              : 'bg-gray-100 hover:bg-gray-200 text-gray-900'
          )}
          {...props}
        >
          {children}
        </button>
      );
    }
  `;
}

// Ideal Tailwind use cases
const tailwindExcellence = {
  landingPages: 'Rapid iteration, design-first',
  marketingSites: 'Consistent branding, fast builds',
  adminDashboards: 'Utility-first speed, less customization',
  componentLibraries: 'When consumers control styling',
  mvpProducts: 'Speed to market over customization'
};

// Ideal CSS-in-JS use cases
const cssInJsExcellence = {
  designSystems: 'Complex variants and TypeScript',
  dashboards: 'Dynamic theming and complex states',
  multiTenantSaas: 'Per-tenant branding requirements',
  interactiveApps: 'Animation and state-driven styling',
  componentLibraries: 'When authoring complex reusable components'
};

// hybrid-approach.ts
export const hybridStrategy = {
  utilities: {
    tool: 'Tailwind',
    useFor: [
      'Layout (flexbox, grid)',
      'Spacing (padding, margins)', 
      'Colors (backgrounds, text)',
      'Typography (sizes, weights)',
      'Basic responsive design'
    ]
  },
  
  components: {
    tool: 'Stitches or Emotion',
    useFor: [
      'Complex component variants',
      'Dynamic theming',
      'Animation and transitions',
      'Advanced pseudo-selectors',
      'Component-specific logic'
    ]
  },
  
  implementation: `
    // Use Tailwind for 80% of styling
    <div className="flex items-center justify-between p-6 bg-white rounded-lg">
      
      // Use CSS-in-JS for complex components
      <StyledButton 
        variant="primary" 
        size="lg"
        isLoading={loading}
        theme={currentTheme}
      >
        Submit
      </StyledButton>
    </div>
  `
};