Component Library Patterns

Design Tokens

// tokens.ts - Single source of truth
export const tokens = {
  color: {
    primary: { 50: '#eff6ff', 500: '#3b82f6', 900: '#1e3a5f' },
    semantic: { success: '#22c55e', error: '#ef4444', warning: '#f59e0b' }
  },
  spacing: { xs: '4px', sm: '8px', md: '16px', lg: '24px', xl: '32px' },
  font: {
    size: { sm: '0.875rem', base: '1rem', lg: '1.125rem', xl: '1.25rem' },
    weight: { normal: 400, medium: 500, semibold: 600, bold: 700 }
  },
  radius: { sm: '4px', md: '8px', lg: '12px', full: '9999px' },
  shadow: {
    sm: '0 1px 2px rgba(0,0,0,0.05)',
    md: '0 4px 6px rgba(0,0,0,0.1)'
  }
} as const

Component API Design

// Composition pattern > prop explosion
// YANLIS:
<Button icon="check" iconPosition="left" loading loadingText="..." />

// DOGRU:
<Button>
  <Button.Icon><CheckIcon /></Button.Icon>
  <Button.Text>Save</Button.Text>
  <Button.Spinner />
</Button>

// Polymorphic component
interface ButtonProps<T extends ElementType = 'button'> {
  as?: T
  variant: 'primary' | 'secondary' | 'ghost'
  size: 'sm' | 'md' | 'lg'
}

Storybook Patterns

// Component.stories.tsx
const meta: Meta<typeof Button> = {
  component: Button,
  argTypes: {
    variant: { control: 'select', options: ['primary', 'secondary'] },
    size: { control: 'radio', options: ['sm', 'md', 'lg'] }
  }
}

export const Playground: Story = { args: { variant: 'primary', children: 'Click' } }
export const AllVariants: Story = {
  render: () => (
    <div style={{ display: 'flex', gap: 8 }}>
      {(['primary', 'secondary', 'ghost'] as const).map(v => (
        <Button key={v} variant={v}>{v}</Button>
      ))}
    </div>
  )
}

Visual Regression Testing