531 lines
12 KiB
Markdown
531 lines
12 KiB
Markdown
---
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name: coding-standards
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description: Universal coding standards, best practices, and patterns for TypeScript, JavaScript, React, and Node.js development.
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origin: ECC
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---
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# Coding Standards & Best Practices
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Universal coding standards applicable across all projects.
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## When to Activate
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- Starting a new project or module
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- Reviewing code for quality and maintainability
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- Refactoring existing code to follow conventions
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- Enforcing naming, formatting, or structural consistency
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- Setting up linting, formatting, or type-checking rules
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- Onboarding new contributors to coding conventions
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## Code Quality Principles
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### 1. Readability First
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- Code is read more than written
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- Clear variable and function names
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- Self-documenting code preferred over comments
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- Consistent formatting
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### 2. KISS (Keep It Simple, Stupid)
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- Simplest solution that works
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- Avoid over-engineering
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- No premature optimization
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- Easy to understand > clever code
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### 3. DRY (Don't Repeat Yourself)
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- Extract common logic into functions
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- Create reusable components
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- Share utilities across modules
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- Avoid copy-paste programming
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### 4. YAGNI (You Aren't Gonna Need It)
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- Don't build features before they're needed
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- Avoid speculative generality
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- Add complexity only when required
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- Start simple, refactor when needed
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## TypeScript/JavaScript Standards
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### Variable Naming
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```typescript
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// ✅ GOOD: Descriptive names
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const marketSearchQuery = 'election'
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const isUserAuthenticated = true
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const totalRevenue = 1000
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// ❌ BAD: Unclear names
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const q = 'election'
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const flag = true
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const x = 1000
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```
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### Function Naming
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```typescript
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// ✅ GOOD: Verb-noun pattern
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async function fetchMarketData(marketId: string) { }
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function calculateSimilarity(a: number[], b: number[]) { }
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function isValidEmail(email: string): boolean { }
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// ❌ BAD: Unclear or noun-only
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async function market(id: string) { }
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function similarity(a, b) { }
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function email(e) { }
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```
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### Immutability Pattern (CRITICAL)
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```typescript
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// ✅ ALWAYS use spread operator
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const updatedUser = {
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...user,
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name: 'New Name'
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}
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const updatedArray = [...items, newItem]
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// ❌ NEVER mutate directly
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user.name = 'New Name' // BAD
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items.push(newItem) // BAD
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```
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### Error Handling
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```typescript
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// ✅ GOOD: Comprehensive error handling
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async function fetchData(url: string) {
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try {
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const response = await fetch(url)
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if (!response.ok) {
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throw new Error(`HTTP ${response.status}: ${response.statusText}`)
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}
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return await response.json()
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} catch (error) {
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console.error('Fetch failed:', error)
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throw new Error('Failed to fetch data')
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}
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}
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// ❌ BAD: No error handling
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async function fetchData(url) {
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const response = await fetch(url)
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return response.json()
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}
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```
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### Async/Await Best Practices
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```typescript
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// ✅ GOOD: Parallel execution when possible
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const [users, markets, stats] = await Promise.all([
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fetchUsers(),
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fetchMarkets(),
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fetchStats()
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])
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// ❌ BAD: Sequential when unnecessary
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const users = await fetchUsers()
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const markets = await fetchMarkets()
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const stats = await fetchStats()
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```
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### Type Safety
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```typescript
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// ✅ GOOD: Proper types
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interface Market {
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id: string
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name: string
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status: 'active' | 'resolved' | 'closed'
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created_at: Date
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}
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function getMarket(id: string): Promise<Market> {
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// Implementation
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}
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// ❌ BAD: Using 'any'
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function getMarket(id: any): Promise<any> {
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// Implementation
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}
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```
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## React Best Practices
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### Component Structure
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```typescript
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// ✅ GOOD: Functional component with types
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interface ButtonProps {
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children: React.ReactNode
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onClick: () => void
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disabled?: boolean
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variant?: 'primary' | 'secondary'
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}
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export function Button({
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children,
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onClick,
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disabled = false,
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variant = 'primary'
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}: ButtonProps) {
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return (
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<button
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onClick={onClick}
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disabled={disabled}
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className={`btn btn-${variant}`}
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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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// ❌ BAD: No types, unclear structure
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export function Button(props) {
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return <button onClick={props.onClick}>{props.children}</button>
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}
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```
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### Custom Hooks
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```typescript
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// ✅ GOOD: Reusable custom hook
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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 debouncedQuery = useDebounce(searchQuery, 500)
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```
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### State Management
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```typescript
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// ✅ GOOD: Proper state updates
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const [count, setCount] = useState(0)
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// Functional update for state based on previous state
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setCount(prev => prev + 1)
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// ❌ BAD: Direct state reference
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setCount(count + 1) // Can be stale in async scenarios
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```
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### Conditional Rendering
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```typescript
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// ✅ GOOD: Clear conditional rendering
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{isLoading && <Spinner />}
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{error && <ErrorMessage error={error} />}
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{data && <DataDisplay data={data} />}
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// ❌ BAD: Ternary hell
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{isLoading ? <Spinner /> : error ? <ErrorMessage error={error} /> : data ? <DataDisplay data={data} /> : null}
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```
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## API Design Standards
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### REST API Conventions
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```
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GET /api/markets # List all markets
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GET /api/markets/:id # Get specific market
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POST /api/markets # Create new market
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PUT /api/markets/:id # Update market (full)
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PATCH /api/markets/:id # Update market (partial)
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DELETE /api/markets/:id # Delete market
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# Query parameters for filtering
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GET /api/markets?status=active&limit=10&offset=0
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```
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### Response Format
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```typescript
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// ✅ GOOD: Consistent response structure
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interface ApiResponse<T> {
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success: boolean
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data?: T
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error?: string
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meta?: {
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total: number
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page: number
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limit: number
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}
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}
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// Success response
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return NextResponse.json({
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success: true,
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data: markets,
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meta: { total: 100, page: 1, limit: 10 }
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})
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// Error response
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return NextResponse.json({
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success: false,
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error: 'Invalid request'
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}, { status: 400 })
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```
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### Input Validation
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```typescript
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import { z } from 'zod'
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// ✅ GOOD: Schema validation
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const CreateMarketSchema = z.object({
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name: z.string().min(1).max(200),
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description: z.string().min(1).max(2000),
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endDate: z.string().datetime(),
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categories: z.array(z.string()).min(1)
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})
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export async function POST(request: Request) {
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const body = await request.json()
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try {
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const validated = CreateMarketSchema.parse(body)
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// Proceed with validated data
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} catch (error) {
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if (error instanceof z.ZodError) {
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return NextResponse.json({
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success: false,
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error: 'Validation failed',
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details: error.errors
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}, { status: 400 })
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}
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}
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}
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```
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## File Organization
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### Project Structure
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```
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src/
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├── app/ # Next.js App Router
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│ ├── api/ # API routes
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│ ├── markets/ # Market pages
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│ └── (auth)/ # Auth pages (route groups)
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├── components/ # React components
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│ ├── ui/ # Generic UI components
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│ ├── forms/ # Form components
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│ └── layouts/ # Layout components
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├── hooks/ # Custom React hooks
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├── lib/ # Utilities and configs
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│ ├── api/ # API clients
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│ ├── utils/ # Helper functions
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│ └── constants/ # Constants
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├── types/ # TypeScript types
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└── styles/ # Global styles
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```
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### File Naming
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```
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components/Button.tsx # PascalCase for components
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hooks/useAuth.ts # camelCase with 'use' prefix
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lib/formatDate.ts # camelCase for utilities
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types/market.types.ts # camelCase with .types suffix
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```
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## Comments & Documentation
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### When to Comment
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```typescript
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// ✅ GOOD: Explain WHY, not WHAT
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// Use exponential backoff to avoid overwhelming the API during outages
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const delay = Math.min(1000 * Math.pow(2, retryCount), 30000)
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// Deliberately using mutation here for performance with large arrays
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items.push(newItem)
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// ❌ BAD: Stating the obvious
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// Increment counter by 1
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count++
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// Set name to user's name
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name = user.name
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```
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### JSDoc for Public APIs
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```typescript
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/**
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* Searches markets using semantic similarity.
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*
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* @param query - Natural language search query
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* @param limit - Maximum number of results (default: 10)
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* @returns Array of markets sorted by similarity score
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* @throws {Error} If OpenAI API fails or Redis unavailable
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*
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* @example
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* ```typescript
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* const results = await searchMarkets('election', 5)
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* console.log(results[0].name) // "Trump vs Biden"
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* ```
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*/
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export async function searchMarkets(
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query: string,
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limit: number = 10
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): Promise<Market[]> {
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// Implementation
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}
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```
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## Performance Best Practices
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### Memoization
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```typescript
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import { useMemo, useCallback } from 'react'
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// ✅ GOOD: Memoize 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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// ✅ GOOD: Memoize callbacks
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const handleSearch = useCallback((query: string) => {
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setSearchQuery(query)
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}, [])
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```
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### Lazy Loading
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```typescript
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import { lazy, Suspense } from 'react'
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// ✅ GOOD: Lazy load heavy components
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const HeavyChart = lazy(() => import('./HeavyChart'))
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export function Dashboard() {
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return (
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<Suspense fallback={<Spinner />}>
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<HeavyChart />
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</Suspense>
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)
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}
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```
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### Database Queries
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```typescript
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// ✅ GOOD: Select only needed columns
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const { data } = await supabase
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.from('markets')
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.select('id, name, status')
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.limit(10)
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// ❌ BAD: Select everything
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const { data } = await supabase
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.from('markets')
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.select('*')
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```
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## Testing Standards
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### Test Structure (AAA Pattern)
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```typescript
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test('calculates similarity correctly', () => {
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// Arrange
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const vector1 = [1, 0, 0]
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const vector2 = [0, 1, 0]
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// Act
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const similarity = calculateCosineSimilarity(vector1, vector2)
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// Assert
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expect(similarity).toBe(0)
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})
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```
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### Test Naming
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```typescript
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// ✅ GOOD: Descriptive test names
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test('returns empty array when no markets match query', () => { })
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test('throws error when OpenAI API key is missing', () => { })
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test('falls back to substring search when Redis unavailable', () => { })
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// ❌ BAD: Vague test names
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test('works', () => { })
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test('test search', () => { })
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```
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## Code Smell Detection
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Watch for these anti-patterns:
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### 1. Long Functions
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```typescript
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// ❌ BAD: Function > 50 lines
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function processMarketData() {
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// 100 lines of code
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}
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// ✅ GOOD: Split into smaller functions
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function processMarketData() {
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const validated = validateData()
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const transformed = transformData(validated)
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return saveData(transformed)
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}
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```
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### 2. Deep Nesting
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```typescript
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// ❌ BAD: 5+ levels of nesting
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if (user) {
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if (user.isAdmin) {
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if (market) {
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if (market.isActive) {
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if (hasPermission) {
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// Do something
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}
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}
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}
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}
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}
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// ✅ GOOD: Early returns
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if (!user) return
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if (!user.isAdmin) return
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if (!market) return
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if (!market.isActive) return
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if (!hasPermission) return
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// Do something
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```
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### 3. Magic Numbers
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```typescript
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// ❌ BAD: Unexplained numbers
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if (retryCount > 3) { }
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setTimeout(callback, 500)
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// ✅ GOOD: Named constants
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const MAX_RETRIES = 3
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const DEBOUNCE_DELAY_MS = 500
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if (retryCount > MAX_RETRIES) { }
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setTimeout(callback, DEBOUNCE_DELAY_MS)
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```
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**Remember**: Code quality is not negotiable. Clear, maintainable code enables rapid development and confident refactoring.
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