632 lines
14 KiB
Markdown
632 lines
14 KiB
Markdown
---
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name: frontend-patterns
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description: Frontend development patterns for React, Next.js, state management, performance optimization, and UI best practices.
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---
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# Frontend Development Patterns
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Modern frontend patterns for React, Next.js, and performant user interfaces.
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## Component Patterns
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### Composition Over Inheritance
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```typescript
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// ✅ GOOD: Component composition
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interface CardProps {
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children: React.ReactNode
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variant?: 'default' | 'outlined'
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}
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export function Card({ children, variant = 'default' }: CardProps) {
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return <div className={`card card-${variant}`}>{children}</div>
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}
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export function CardHeader({ children }: { children: React.ReactNode }) {
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return <div className="card-header">{children}</div>
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}
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export function CardBody({ children }: { children: React.ReactNode }) {
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return <div className="card-body">{children}</div>
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}
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// Usage
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<Card>
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<CardHeader>Title</CardHeader>
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<CardBody>Content</CardBody>
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</Card>
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```
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### Compound Components
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```typescript
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interface TabsContextValue {
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activeTab: string
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setActiveTab: (tab: string) => void
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}
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const TabsContext = createContext<TabsContextValue | undefined>(undefined)
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export function Tabs({ children, defaultTab }: {
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children: React.ReactNode
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defaultTab: string
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}) {
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const [activeTab, setActiveTab] = useState(defaultTab)
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return (
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<TabsContext.Provider value={{ activeTab, setActiveTab }}>
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{children}
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</TabsContext.Provider>
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)
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}
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export function TabList({ children }: { children: React.ReactNode }) {
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return <div className="tab-list">{children}</div>
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}
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export function Tab({ id, children }: { id: string, children: React.ReactNode }) {
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const context = useContext(TabsContext)
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if (!context) throw new Error('Tab must be used within Tabs')
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return (
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<button
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className={context.activeTab === id ? 'active' : ''}
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onClick={() => context.setActiveTab(id)}
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>
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{children}
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</button>
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)
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}
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// Usage
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<Tabs defaultTab="overview">
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<TabList>
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<Tab id="overview">Overview</Tab>
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<Tab id="details">Details</Tab>
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</TabList>
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</Tabs>
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```
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### Render Props Pattern
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```typescript
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interface DataLoaderProps<T> {
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url: string
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children: (data: T | null, loading: boolean, error: Error | null) => React.ReactNode
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}
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export function DataLoader<T>({ url, children }: DataLoaderProps<T>) {
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const [data, setData] = useState<T | null>(null)
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const [loading, setLoading] = useState(true)
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const [error, setError] = useState<Error | null>(null)
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useEffect(() => {
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fetch(url)
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.then(res => res.json())
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.then(setData)
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.catch(setError)
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.finally(() => setLoading(false))
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}, [url])
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return <>{children(data, loading, error)}</>
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}
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// Usage
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<DataLoader<Market[]> url="/api/markets">
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{(markets, loading, error) => {
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if (loading) return <Spinner />
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if (error) return <Error error={error} />
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return <MarketList markets={markets!} />
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}}
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</DataLoader>
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```
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## Custom Hooks Patterns
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### State Management Hook
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```typescript
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export function useToggle(initialValue = false): [boolean, () => void] {
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const [value, setValue] = useState(initialValue)
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const toggle = useCallback(() => {
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setValue(v => !v)
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}, [])
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return [value, toggle]
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}
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// Usage
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const [isOpen, toggleOpen] = useToggle()
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```
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### Async Data Fetching Hook
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```typescript
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interface UseQueryOptions<T> {
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onSuccess?: (data: T) => void
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onError?: (error: Error) => void
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enabled?: boolean
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}
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export function useQuery<T>(
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key: string,
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fetcher: () => Promise<T>,
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options?: UseQueryOptions<T>
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) {
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const [data, setData] = useState<T | null>(null)
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const [error, setError] = useState<Error | null>(null)
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const [loading, setLoading] = useState(false)
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const refetch = useCallback(async () => {
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setLoading(true)
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setError(null)
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try {
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const result = await fetcher()
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setData(result)
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options?.onSuccess?.(result)
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} catch (err) {
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const error = err as Error
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setError(error)
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options?.onError?.(error)
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} finally {
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setLoading(false)
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}
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}, [fetcher, options])
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useEffect(() => {
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if (options?.enabled !== false) {
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refetch()
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}
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}, [key, refetch, options?.enabled])
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return { data, error, loading, refetch }
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}
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// Usage
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const { data: markets, loading, error, refetch } = useQuery(
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'markets',
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() => fetch('/api/markets').then(r => r.json()),
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{
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onSuccess: data => console.log('Fetched', data.length, 'markets'),
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onError: err => console.error('Failed:', err)
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}
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)
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```
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### Debounce Hook
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```typescript
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export function useDebounce<T>(value: T, delay: number): T {
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const [debouncedValue, setDebouncedValue] = useState<T>(value)
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useEffect(() => {
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const handler = setTimeout(() => {
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setDebouncedValue(value)
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}, delay)
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return () => clearTimeout(handler)
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}, [value, delay])
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return debouncedValue
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}
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// Usage
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const [searchQuery, setSearchQuery] = useState('')
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const debouncedQuery = useDebounce(searchQuery, 500)
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useEffect(() => {
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if (debouncedQuery) {
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performSearch(debouncedQuery)
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}
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}, [debouncedQuery])
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```
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## State Management Patterns
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### Context + Reducer Pattern
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```typescript
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interface State {
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markets: Market[]
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selectedMarket: Market | null
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loading: boolean
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}
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type Action =
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| { type: 'SET_MARKETS'; payload: Market[] }
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| { type: 'SELECT_MARKET'; payload: Market }
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| { type: 'SET_LOADING'; payload: boolean }
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function reducer(state: State, action: Action): State {
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switch (action.type) {
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case 'SET_MARKETS':
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return { ...state, markets: action.payload }
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case 'SELECT_MARKET':
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return { ...state, selectedMarket: action.payload }
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case 'SET_LOADING':
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return { ...state, loading: action.payload }
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default:
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return state
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}
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}
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const MarketContext = createContext<{
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state: State
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dispatch: Dispatch<Action>
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} | undefined>(undefined)
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export function MarketProvider({ children }: { children: React.ReactNode }) {
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const [state, dispatch] = useReducer(reducer, {
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markets: [],
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selectedMarket: null,
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loading: false
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})
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return (
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<MarketContext.Provider value={{ state, dispatch }}>
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{children}
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</MarketContext.Provider>
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)
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}
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export function useMarkets() {
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const context = useContext(MarketContext)
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if (!context) throw new Error('useMarkets must be used within MarketProvider')
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return context
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}
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```
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## Performance Optimization
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### Memoization
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```typescript
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// ✅ useMemo for expensive computations
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const sortedMarkets = useMemo(() => {
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return markets.sort((a, b) => b.volume - a.volume)
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}, [markets])
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// ✅ useCallback for functions passed to children
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const handleSearch = useCallback((query: string) => {
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setSearchQuery(query)
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}, [])
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// ✅ React.memo for pure components
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export const MarketCard = React.memo<MarketCardProps>(({ market }) => {
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return (
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<div className="market-card">
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<h3>{market.name}</h3>
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<p>{market.description}</p>
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</div>
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)
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})
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```
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### Code Splitting & Lazy Loading
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```typescript
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import { lazy, Suspense } from 'react'
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// ✅ Lazy load heavy components
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const HeavyChart = lazy(() => import('./HeavyChart'))
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const ThreeJsBackground = lazy(() => import('./ThreeJsBackground'))
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export function Dashboard() {
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return (
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<div>
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<Suspense fallback={<ChartSkeleton />}>
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<HeavyChart data={data} />
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</Suspense>
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<Suspense fallback={null}>
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<ThreeJsBackground />
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</Suspense>
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</div>
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)
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}
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```
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### Virtualization for Long Lists
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```typescript
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import { useVirtualizer } from '@tanstack/react-virtual'
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export function VirtualMarketList({ markets }: { markets: Market[] }) {
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const parentRef = useRef<HTMLDivElement>(null)
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const virtualizer = useVirtualizer({
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count: markets.length,
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getScrollElement: () => parentRef.current,
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estimateSize: () => 100, // Estimated row height
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overscan: 5 // Extra items to render
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})
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return (
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<div ref={parentRef} style={{ height: '600px', overflow: 'auto' }}>
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<div
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style={{
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height: `${virtualizer.getTotalSize()}px`,
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position: 'relative'
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}}
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>
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{virtualizer.getVirtualItems().map(virtualRow => (
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<div
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key={virtualRow.index}
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style={{
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position: 'absolute',
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top: 0,
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left: 0,
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width: '100%',
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height: `${virtualRow.size}px`,
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transform: `translateY(${virtualRow.start}px)`
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}}
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>
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<MarketCard market={markets[virtualRow.index]} />
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</div>
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))}
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</div>
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</div>
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)
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}
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```
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## Form Handling Patterns
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### Controlled Form with Validation
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```typescript
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interface FormData {
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name: string
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description: string
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endDate: string
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}
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interface FormErrors {
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name?: string
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description?: string
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endDate?: string
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}
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export function CreateMarketForm() {
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const [formData, setFormData] = useState<FormData>({
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name: '',
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description: '',
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endDate: ''
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})
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const [errors, setErrors] = useState<FormErrors>({})
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const validate = (): boolean => {
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const newErrors: FormErrors = {}
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if (!formData.name.trim()) {
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newErrors.name = 'Name is required'
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} else if (formData.name.length > 200) {
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newErrors.name = 'Name must be under 200 characters'
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}
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if (!formData.description.trim()) {
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newErrors.description = 'Description is required'
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}
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if (!formData.endDate) {
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newErrors.endDate = 'End date is required'
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}
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setErrors(newErrors)
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return Object.keys(newErrors).length === 0
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}
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const handleSubmit = async (e: React.FormEvent) => {
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e.preventDefault()
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if (!validate()) return
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try {
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await createMarket(formData)
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// Success handling
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} catch (error) {
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// Error handling
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}
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}
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return (
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<form onSubmit={handleSubmit}>
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<input
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value={formData.name}
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onChange={e => setFormData(prev => ({ ...prev, name: e.target.value }))}
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placeholder="Market name"
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/>
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{errors.name && <span className="error">{errors.name}</span>}
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{/* Other fields */}
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<button type="submit">Create Market</button>
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</form>
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)
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}
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```
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## Error Boundary Pattern
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```typescript
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interface ErrorBoundaryState {
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hasError: boolean
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error: Error | null
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}
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export class ErrorBoundary extends React.Component<
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{ children: React.ReactNode },
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ErrorBoundaryState
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> {
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state: ErrorBoundaryState = {
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hasError: false,
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error: null
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}
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static getDerivedStateFromError(error: Error): ErrorBoundaryState {
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return { hasError: true, error }
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}
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componentDidCatch(error: Error, errorInfo: React.ErrorInfo) {
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console.error('Error boundary caught:', error, errorInfo)
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}
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render() {
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if (this.state.hasError) {
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return (
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<div className="error-fallback">
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<h2>Something went wrong</h2>
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<p>{this.state.error?.message}</p>
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<button onClick={() => this.setState({ hasError: false })}>
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Try again
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</button>
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</div>
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)
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}
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return this.props.children
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}
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}
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// Usage
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<ErrorBoundary>
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<App />
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</ErrorBoundary>
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```
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## Animation Patterns
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### Framer Motion Animations
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```typescript
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import { motion, AnimatePresence } from 'framer-motion'
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// ✅ List animations
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export function AnimatedMarketList({ markets }: { markets: Market[] }) {
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return (
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<AnimatePresence>
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{markets.map(market => (
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<motion.div
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key={market.id}
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initial={{ opacity: 0, y: 20 }}
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animate={{ opacity: 1, y: 0 }}
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exit={{ opacity: 0, y: -20 }}
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transition={{ duration: 0.3 }}
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>
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<MarketCard market={market} />
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</motion.div>
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))}
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</AnimatePresence>
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)
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}
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// ✅ Modal animations
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export function Modal({ isOpen, onClose, children }: ModalProps) {
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return (
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<AnimatePresence>
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{isOpen && (
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<>
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<motion.div
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className="modal-overlay"
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initial={{ opacity: 0 }}
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animate={{ opacity: 1 }}
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exit={{ opacity: 0 }}
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onClick={onClose}
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/>
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<motion.div
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className="modal-content"
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initial={{ opacity: 0, scale: 0.9, y: 20 }}
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animate={{ opacity: 1, scale: 1, y: 0 }}
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exit={{ opacity: 0, scale: 0.9, y: 20 }}
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>
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{children}
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</motion.div>
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</>
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)}
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</AnimatePresence>
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)
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}
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```
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## Accessibility Patterns
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### Keyboard Navigation
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```typescript
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export function Dropdown({ options, onSelect }: DropdownProps) {
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const [isOpen, setIsOpen] = useState(false)
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const [activeIndex, setActiveIndex] = useState(0)
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const handleKeyDown = (e: React.KeyboardEvent) => {
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switch (e.key) {
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case 'ArrowDown':
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e.preventDefault()
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setActiveIndex(i => Math.min(i + 1, options.length - 1))
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break
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case 'ArrowUp':
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e.preventDefault()
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setActiveIndex(i => Math.max(i - 1, 0))
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break
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case 'Enter':
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e.preventDefault()
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onSelect(options[activeIndex])
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setIsOpen(false)
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break
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case 'Escape':
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setIsOpen(false)
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break
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}
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}
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return (
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<div
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role="combobox"
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aria-expanded={isOpen}
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aria-haspopup="listbox"
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onKeyDown={handleKeyDown}
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>
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{/* Dropdown implementation */}
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</div>
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)
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}
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```
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### Focus Management
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```typescript
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export function Modal({ isOpen, onClose, children }: ModalProps) {
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const modalRef = useRef<HTMLDivElement>(null)
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const previousFocusRef = useRef<HTMLElement | null>(null)
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useEffect(() => {
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if (isOpen) {
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// Save currently focused element
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previousFocusRef.current = document.activeElement as HTMLElement
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// Focus modal
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modalRef.current?.focus()
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} else {
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// Restore focus when closing
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previousFocusRef.current?.focus()
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}
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}, [isOpen])
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return isOpen ? (
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<div
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ref={modalRef}
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role="dialog"
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aria-modal="true"
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tabIndex={-1}
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onKeyDown={e => e.key === 'Escape' && onClose()}
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>
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{children}
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</div>
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) : null
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}
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```
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**Remember**: Modern frontend patterns enable maintainable, performant user interfaces. Choose patterns that fit your project complexity.
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