UI Component Builder

Expert skill for building production-ready UI components for component libraries. Specializes in React, Vue, and Svelte with TypeScript, implementing advanced patterns, animations, and ensuring accessibility and performance.

Core Capabilities

1. Component Creation

• Create new components from scratch with TypeScript
• Implement compound components pattern
• Build components with render props
• Create custom hooks and composables
• Support for polymorphic components (as prop pattern)
• Generic component types for maximum reusability

2. Framework Conversion

Convert components seamlessly between frameworks:

• React → Vue: JSX to template/composition API
• React → Svelte: Hooks to reactive declarations
• Vue → React: Template to JSX, composables to hooks
• Svelte → React: Reactive syntax to useState/useEffect

Preserve functionality, props interface, and behavior while adapting to framework idioms.

3. Advanced Patterns Implementation

Compound Components

// Parent component manages shared state
// Child components access via context
<Select>
  <Select.Trigger />
  <Select.Content>
    <Select.Item value="1">Option 1</Select.Item>
  </Select.Content>
</Select>

Render Props

<DataFetcher url="/api/data">
  {({ data, loading, error }) => (
    // Render logic here
  )}
</DataFetcher>

Custom Hooks Pattern

// Extract reusable logic
const { isOpen, open, close, toggle } = useDisclosure()

4. Animation Integration

• Integrate Framer Motion for React components
• Use transition/animation APIs for Vue/Svelte
• Create spring physics animations
• Implement gesture controls (drag, hover, tap)
• Build enter/exit animations
• Orchestrate complex animation sequences
• Optimize for 60fps performance

5. TypeScript Excellence

• Strict type safety with proper generic constraints
• Discriminated unions for component variants
• Type inference for props and state
• Utility types (Omit, Pick, Required, Partial)
• Type guards and narrowing
• Proper typing for refs, events, and children

6. Accessibility (a11y) First

• Semantic HTML elements
• ARIA attributes when needed (roles, labels, states)
• Keyboard navigation (Tab, Enter, Escape, Arrow keys)
• Focus management and focus trapping
• Screen reader announcements
• Color contrast compliance (WCAG AA/AAA)
• Reduced motion support

7. Performance Optimization

• React.memo / Vue computed / Svelte reactive statements
• useMemo, useCallback optimization
• Virtual scrolling for large lists
• Code splitting and lazy loading
• Bundle size analysis
• Avoid unnecessary re-renders
• Optimize event handlers

Workflow

Phase 1: Analysis & Planning

1. Understand Requirements

   • Component purpose and use cases
   • Required props and variants
   • Accessibility requirements
   • Animation needs
   • Performance constraints

2. Review Existing Code

   • Check for similar components
   • Identify reusable patterns
   • Review design system tokens
   • Check naming conventions

3. Plan Implementation

   • Choose appropriate patterns
   • Define component API (props interface)
   • Plan state management approach
   • Identify edge cases

Phase 2: Implementation

1. Create Base Structure

   • Set up component file(s)
   • Define TypeScript interfaces
   • Implement basic rendering
   • Add prop validation

2. Implement Core Logic

   • Add state management
   • Implement event handlers
   • Apply business logic
   • Handle edge cases

3. Add Styling

   • Use design system tokens
   • Implement variants (size, color, state)
   • Add responsive behavior
   • Support theming (light/dark)

4. Enhance with Features

   • Add animations if needed
   • Implement keyboard navigation
   • Add ARIA attributes
   • Create controlled/uncontrolled variants

Phase 3: Quality Assurance

1. Accessibility Check

   • Test keyboard navigation
   • Verify ARIA attributes
   • Check screen reader output
   • Validate color contrast

2. Performance Review

   • Check for unnecessary renders
   • Optimize heavy computations
   • Review bundle impact
   • Test with React DevTools Profiler

3. Type Safety Verification

   • No TypeScript errors
   • Props are properly typed
   • Type inference works correctly
   • Generic constraints are sound

4. Cross-browser Testing

   • Modern browsers support
   • Graceful degradation
   • Polyfills if needed

Component Patterns Library

Button Component Template

import { forwardRef, type ButtonHTMLAttributes } from 'react'
import { cva, type VariantProps } from 'class-variance-authority'

const buttonVariants = cva(
  'inline-flex items-center justify-center rounded-md font-medium transition-colors focus-visible:outline-none focus-visible:ring-2 disabled:pointer-events-none disabled:opacity-50',
  {
    variants: {
      variant: {
        default: 'bg-primary text-primary-foreground hover:bg-primary/90',
        outline: 'border border-input bg-background hover:bg-accent',
        ghost: 'hover:bg-accent hover:text-accent-foreground',
      },
      size: {
        default: 'h-10 px-4 py-2',
        sm: 'h-9 rounded-md px-3',
        lg: 'h-11 rounded-md px-8',
      },
    },
    defaultVariants: {
      variant: 'default',
      size: 'default',
    },
  }
)

interface ButtonProps
  extends ButtonHTMLAttributes<HTMLButtonElement>,
    VariantProps<typeof buttonVariants> {
  asChild?: boolean
}

const Button = forwardRef<HTMLButtonElement, ButtonProps>(
  ({ className, variant, size, ...props }, ref) => {
    return (
      <button
        ref={ref}
        className={buttonVariants({ variant, size, className })}
        {...props}
      />
    )
  }
)

Button.displayName = 'Button'

export { Button, buttonVariants }

Compound Component Template

import { createContext, useContext, useState } from 'react'

interface TabsContextValue {
  activeTab: string
  setActiveTab: (tab: string) => void
}

const TabsContext = createContext<TabsContextValue | undefined>(undefined)

export function Tabs({ defaultValue, children }: TabsProps) {
  const [activeTab, setActiveTab] = useState(defaultValue)

  return (
    <TabsContext.Provider value={{ activeTab, setActiveTab }}>
      <div>{children}</div>
    </TabsContext.Provider>
  )
}

export function TabsList({ children }: TabsListProps) {
  return <div role="tablist">{children}</div>
}

export function TabsTrigger({ value, children }: TabsTriggerProps) {
  const context = useContext(TabsContext)
  const isActive = context?.activeTab === value

  return (
    <button
      role="tab"
      aria-selected={isActive}
      onClick={() => context?.setActiveTab(value)}
    >
      {children}
    </button>
  )
}

export function TabsContent({ value, children }: TabsContentProps) {
  const context = useContext(TabsContext)
  if (context?.activeTab !== value) return null

  return <div role="tabpanel">{children}</div>
}

Animated Component Template (Framer Motion)

import { motion, AnimatePresence } from 'framer-motion'
import { useState } from 'react'

export function Modal({ isOpen, onClose, children }: ModalProps) {
  return (
    <AnimatePresence>
      {isOpen && (
        <>
          <motion.div
            initial={{ opacity: 0 }}
            animate={{ opacity: 1 }}
            exit={{ opacity: 0 }}
            onClick={onClose}
            className="fixed inset-0 bg-black/50"
          />
          <motion.div
            initial={{ opacity: 0, scale: 0.95, y: 20 }}
            animate={{ opacity: 1, scale: 1, y: 0 }}
            exit={{ opacity: 0, scale: 0.95, y: 20 }}
            transition={{ type: 'spring', duration: 0.3 }}
            className="fixed inset-0 flex items-center justify-center"
          >
            <div className="bg-white rounded-lg p-6 max-w-md w-full">
              {children}
            </div>
          </motion.div>
        </>
      )}
    </AnimatePresence>
  )
}

Framework Conversion Guidelines

React to Vue Conversion

// REACT
function Counter() {
  const [count, setCount] = useState(0)
  useEffect(() => {
    console.log('Count changed:', count)
  }, [count])

  return <button onClick={() => setCount(c => c + 1)}>{count}</button>
}

// VUE (Composition API)
<script setup lang="ts">
import { ref, watch } from 'vue'

const count = ref(0)

watch(count, (newCount) => {
  console.log('Count changed:', newCount)
})
</script>

<template>
  <button @click="count++">{{ count }}</button>
</template>

React to Svelte Conversion

// REACT
function Counter() {
  const [count, setCount] = useState(0)

  return <button onClick={() => setCount(c => c + 1)}>{count}</button>
}

// SVELTE
<script lang="ts">
  let count = 0

  $: console.log('Count changed:', count)
</script>

<button on:click={() => count++}>
  {count}
</button>

Best Practices

Component Structure

• One component per file (with related subcomponents)
• Co-locate types, styles, and utilities
• Export component as named export
• Provide displayName for debugging

Props Design

• Keep props interface simple and focused
• Use discriminated unions for variants
• Provide sensible defaults
• Support both controlled and uncontrolled modes
• Accept className for style overrides
• Forward refs when wrapping native elements

State Management

• Lift state up when needed by multiple components
• Keep component-specific state local
• Use context sparingly (avoid prop drilling)
• Prefer composition over context

Naming Conventions

• PascalCase for components
• camelCase for props and functions
• SCREAMING_SNAKE_CASE for constants
• Prefix custom hooks with "use"
• Prefix event handlers with "handle" or "on"

File Organization

components/
  Button/
    Button.tsx           # Main component
    Button.types.ts      # Type definitions
    Button.styles.ts     # Styling (if separate)
    Button.test.tsx      # Unit tests
    index.ts             # Public exports

Accessibility Checklist

• Semantic HTML elements used
• Keyboard navigation works
• Focus visible and manageable
• ARIA attributes where needed
• Screen reader tested
• Color contrast meets WCAG AA
• Supports prefers-reduced-motion

Performance Checklist

• No unnecessary re-renders
• Heavy computations memoized
• Event handlers optimized
• Bundle size impact minimal
• Lazy loading where appropriate
• Virtual scrolling for large lists

Common Patterns

Polymorphic Component (as prop)

type AsProp<C extends React.ElementType> = {
  as?: C
}

type PropsToOmit<C extends React.ElementType, P> = keyof (AsProp<C> & P)

type PolymorphicComponentProp<
  C extends React.ElementType,
  Props = {}
> = React.PropsWithChildren<Props & AsProp<C>> &
  Omit<React.ComponentPropsWithoutRef<C>, PropsToOmit<C, Props>>

type TextProps<C extends React.ElementType> = PolymorphicComponentProp<
  C,
  { color?: 'primary' | 'secondary' }
>

export function Text<C extends React.ElementType = 'span'>({
  as,
  color = 'primary',
  children,
  ...props
}: TextProps<C>) {
  const Component = as || 'span'
  return <Component className={color} {...props}>{children}</Component>
}

// Usage: <Text as="h1">Title</Text>

Controlled/Uncontrolled Pattern

interface InputProps {
  value?: string              // Controlled
  defaultValue?: string       // Uncontrolled
  onChange?: (value: string) => void
}

function Input({ value, defaultValue, onChange }: InputProps) {
  const [internalValue, setInternalValue] = useState(defaultValue ?? '')

  const isControlled = value !== undefined
  const currentValue = isControlled ? value : internalValue

  const handleChange = (e: React.ChangeEvent<HTMLInputElement>) => {
    const newValue = e.target.value
    if (!isControlled) {
      setInternalValue(newValue)
    }
    onChange?.(newValue)
  }

  return <input value={currentValue} onChange={handleChange} />
}

Focus Trap (for Modals)

import { useEffect, useRef } from 'react'

function useFocusTrap(isActive: boolean) {
  const containerRef = useRef<HTMLDivElement>(null)

  useEffect(() => {
    if (!isActive) return

    const container = containerRef.current
    if (!container) return

    const focusableElements = container.querySelectorAll(
      'a[href], button, textarea, input, select, [tabindex]:not([tabindex="-1"])'
    )

    const firstElement = focusableElements[0] as HTMLElement
    const lastElement = focusableElements[focusableElements.length - 1] as HTMLElement

    const handleTab = (e: KeyboardEvent) => {
      if (e.key !== 'Tab') return

      if (e.shiftKey && document.activeElement === firstElement) {
        e.preventDefault()
        lastElement.focus()
      } else if (!e.shiftKey && document.activeElement === lastElement) {
        e.preventDefault()
        firstElement.focus()
      }
    }

    container.addEventListener('keydown', handleTab)
    firstElement?.focus()

    return () => container.removeEventListener('keydown', handleTab)
  }, [isActive])

  return containerRef
}

Tools & Dependencies

Essential Tools

• TypeScript: Type safety and better DX
• class-variance-authority (cva): Variant management
• clsx / cn: Conditional className composition
• Framer Motion: Advanced animations
• React Hook Form: Form state management
• Zod: Runtime validation

Development Tools

• Vite: Fast development server
• tsup: TypeScript bundler
• Vitest: Testing framework
• React Testing Library: Component testing
• Storybook: Component development

Tips for Success

1. Start Simple: Build basic functionality first, then add complexity
2. Think in Components: Break down complex UIs into smaller pieces
3. Composition Over Inheritance: Use composition patterns
4. Test Early: Write tests as you build
5. Document Props: Add JSDoc comments for prop descriptions
6. Use Design Tokens: Reference design system values
7. Consider Edge Cases: Empty states, loading, errors
8. Mobile First: Design for mobile, enhance for desktop
9. Performance Budget: Keep bundle size in check
10. Accessibility Always: Build accessible from the start

When to Use This Skill

Activate this skill when you need to:

• Create new UI components from scratch
• Convert components between React/Vue/Svelte
• Implement advanced component patterns
• Add animations to components
• Optimize component performance
• Improve component accessibility
• Refactor existing components
• Build compound components
• Create polymorphic components
• Implement custom hooks/composables

Output Format

When creating components, provide:

1. Complete Component Code: Fully typed and production-ready
2. Usage Example: Show how to use the component
3. Props Documentation: Describe all props with types
4. Accessibility Notes: Keyboard shortcuts and ARIA usage
5. Performance Tips: Any optimization considerations
6. Styling Notes: How to customize appearance

Always follow the project's existing conventions and patterns.