Coding Standards & Best Practices

Universal coding standards applicable across all projects.

Code Quality Principles

1. Readability First

• Code is read more than written
• Clear variable and function names
• Self-documenting code preferred over comments
• Consistent formatting

2. KISS (Keep It Simple, Stupid)

• Simplest solution that works
• Avoid over-engineering
• No premature optimization
• Easy to understand > clever code

3. DRY (Don't Repeat Yourself)

• Extract common logic into functions
• Create reusable components
• Share utilities across modules
• Avoid copy-paste programming

4. YAGNI (You Aren't Gonna Need It)

• Don't build features before they're needed
• Avoid speculative generality
• Add complexity only when required
• Start simple, refactor when needed

TypeScript/JavaScript Standards

Variable Naming

typescript
1// ✅ GOOD: Descriptive names
2const marketSearchQuery = 'election'
3const isUserAuthenticated = true
4const totalRevenue = 1000
5
6// ❌ BAD: Unclear names
7const q = 'election'
8const flag = true
9const x = 1000

Function Naming

typescript
1// ✅ GOOD: Verb-noun pattern
2async function fetchMarketData(marketId: string) { }
3function calculateSimilarity(a: number[], b: number[]) { }
4function isValidEmail(email: string): boolean { }
5
6// ❌ BAD: Unclear or noun-only
7async function market(id: string) { }
8function similarity(a, b) { }
9function email(e) { }

Immutability Pattern (CRITICAL)

typescript
1// ✅ ALWAYS use spread operator
2const updatedUser = {
3  ...user,
4  name: 'New Name'
5}
6
7const updatedArray = [...items, newItem]
8
9// ❌ NEVER mutate directly
10user.name = 'New Name'  // BAD
11items.push(newItem)     // BAD

Error Handling

typescript
1// ✅ GOOD: Comprehensive error handling
2async function fetchData(url: string) {
3  try {
4    const response = await fetch(url)
5
6    if (!response.ok) {
7      throw new Error(`HTTP ${response.status}: ${response.statusText}`)
8    }
9
10    return await response.json()
11  } catch (error) {
12    console.error('Fetch failed:', error)
13    throw new Error('Failed to fetch data')
14  }
15}
16
17// ❌ BAD: No error handling
18async function fetchData(url) {
19  const response = await fetch(url)
20  return response.json()
21}

Async/Await Best Practices

typescript
1// ✅ GOOD: Parallel execution when possible
2const [users, markets, stats] = await Promise.all([
3  fetchUsers(),
4  fetchMarkets(),
5  fetchStats()
6])
7
8// ❌ BAD: Sequential when unnecessary
9const users = await fetchUsers()
10const markets = await fetchMarkets()
11const stats = await fetchStats()

Type Safety

typescript
1// ✅ GOOD: Proper types
2interface Market {
3  id: string
4  name: string
5  status: 'active' | 'resolved' | 'closed'
6  created_at: Date
7}
8
9function getMarket(id: string): Promise<Market> {
10  // Implementation
11}
12
13// ❌ BAD: Using 'any'
14function getMarket(id: any): Promise<any> {
15  // Implementation
16}

React Best Practices

Component Structure

typescript
1// ✅ GOOD: Functional component with types
2interface ButtonProps {
3  children: React.ReactNode
4  onClick: () => void
5  disabled?: boolean
6  variant?: 'primary' | 'secondary'
7}
8
9export function Button({
10  children,
11  onClick,
12  disabled = false,
13  variant = 'primary'
14}: ButtonProps) {
15  return (
16    <button
17      onClick={onClick}
18      disabled={disabled}
19      className={`btn btn-${variant}`}
20    >
21      {children}
22    </button>
23  )
24}
25
26// ❌ BAD: No types, unclear structure
27export function Button(props) {
28  return <button onClick={props.onClick}>{props.children}</button>
29}

Custom Hooks

typescript
1// ✅ GOOD: Reusable custom hook
2export function useDebounce<T>(value: T, delay: number): T {
3  const [debouncedValue, setDebouncedValue] = useState<T>(value)
4
5  useEffect(() => {
6    const handler = setTimeout(() => {
7      setDebouncedValue(value)
8    }, delay)
9
10    return () => clearTimeout(handler)
11  }, [value, delay])
12
13  return debouncedValue
14}
15
16// Usage
17const debouncedQuery = useDebounce(searchQuery, 500)

State Management

typescript
1// ✅ GOOD: Proper state updates
2const [count, setCount] = useState(0)
3
4// Functional update for state based on previous state
5setCount(prev => prev + 1)
6
7// ❌ BAD: Direct state reference
8setCount(count + 1)  // Can be stale in async scenarios

Conditional Rendering

typescript
1// ✅ GOOD: Clear conditional rendering
2{isLoading && <Spinner />}
3{error && <ErrorMessage error={error} />}
4{data && <DataDisplay data={data} />}
5
6// ❌ BAD: Ternary hell
7{isLoading ? <Spinner /> : error ? <ErrorMessage error={error} /> : data ? <DataDisplay data={data} /> : null}

API Design Standards

REST API Conventions

GET    /api/markets              # List all markets
GET    /api/markets/:id          # Get specific market
POST   /api/markets              # Create new market
PUT    /api/markets/:id          # Update market (full)
PATCH  /api/markets/:id          # Update market (partial)
DELETE /api/markets/:id          # Delete market

# Query parameters for filtering
GET /api/markets?status=active&limit=10&offset=0

Response Format

typescript
1// ✅ GOOD: Consistent response structure
2interface ApiResponse<T> {
3  success: boolean
4  data?: T
5  error?: string
6  meta?: {
7    total: number
8    page: number
9    limit: number
10  }
11}
12
13// Success response
14return NextResponse.json({
15  success: true,
16  data: markets,
17  meta: { total: 100, page: 1, limit: 10 }
18})
19
20// Error response
21return NextResponse.json({
22  success: false,
23  error: 'Invalid request'
24}, { status: 400 })

Input Validation

typescript
1import { z } from 'zod'
2
3// ✅ GOOD: Schema validation
4const CreateMarketSchema = z.object({
5  name: z.string().min(1).max(200),
6  description: z.string().min(1).max(2000),
7  endDate: z.string().datetime(),
8  categories: z.array(z.string()).min(1)
9})
10
11export async function POST(request: Request) {
12  const body = await request.json()
13
14  try {
15    const validated = CreateMarketSchema.parse(body)
16    // Proceed with validated data
17  } catch (error) {
18    if (error instanceof z.ZodError) {
19      return NextResponse.json({
20        success: false,
21        error: 'Validation failed',
22        details: error.errors
23      }, { status: 400 })
24    }
25  }
26}

File Organization

Project Structure

src/
├── app/                    # Next.js App Router
│   ├── api/               # API routes
│   ├── markets/           # Market pages
│   └── (auth)/           # Auth pages (route groups)
├── components/            # React components
│   ├── ui/               # Generic UI components
│   ├── forms/            # Form components
│   └── layouts/          # Layout components
├── hooks/                # Custom React hooks
├── lib/                  # Utilities and configs
│   ├── api/             # API clients
│   ├── utils/           # Helper functions
│   └── constants/       # Constants
├── types/                # TypeScript types
└── styles/              # Global styles

File Naming

components/Button.tsx          # PascalCase for components
hooks/useAuth.ts              # camelCase with 'use' prefix
lib/formatDate.ts             # camelCase for utilities
types/market.types.ts         # camelCase with .types suffix

Comments & Documentation

When to Comment

typescript
1// ✅ GOOD: Explain WHY, not WHAT
2// Use exponential backoff to avoid overwhelming the API during outages
3const delay = Math.min(1000 * Math.pow(2, retryCount), 30000)
4
5// Deliberately using mutation here for performance with large arrays
6items.push(newItem)
7
8// ❌ BAD: Stating the obvious
9// Increment counter by 1
10count++
11
12// Set name to user's name
13name = user.name

JSDoc for Public APIs

typescript
1/**
2 * Searches markets using semantic similarity.
3 *
4 * @param query - Natural language search query
5 * @param limit - Maximum number of results (default: 10)
6 * @returns Array of markets sorted by similarity score
7 * @throws {Error} If OpenAI API fails or Redis unavailable
8 *
9 * @example
10 * ```typescript
11 * const results = await searchMarkets('election', 5)
12 * console.log(results[0].name) // "Trump vs Biden"
13 * ```
14 */
15export async function searchMarkets(
16  query: string,
17  limit: number = 10
18): Promise<Market[]> {
19  // Implementation
20}

Performance Best Practices

Memoization

typescript
1import { useMemo, useCallback } from 'react'
2
3// ✅ GOOD: Memoize expensive computations
4const sortedMarkets = useMemo(() => {
5  return markets.sort((a, b) => b.volume - a.volume)
6}, [markets])
7
8// ✅ GOOD: Memoize callbacks
9const handleSearch = useCallback((query: string) => {
10  setSearchQuery(query)
11}, [])

Lazy Loading

typescript
1import { lazy, Suspense } from 'react'
2
3// ✅ GOOD: Lazy load heavy components
4const HeavyChart = lazy(() => import('./HeavyChart'))
5
6export function Dashboard() {
7  return (
8    <Suspense fallback={<Spinner />}>
9      <HeavyChart />
10    </Suspense>
11  )
12}

Database Queries

typescript
1// ✅ GOOD: Select only needed columns
2const { data } = await supabase
3  .from('markets')
4  .select('id, name, status')
5  .limit(10)
6
7// ❌ BAD: Select everything
8const { data } = await supabase
9  .from('markets')
10  .select('*')

Testing Standards

Test Structure (AAA Pattern)

typescript
1test('calculates similarity correctly', () => {
2  // Arrange
3  const vector1 = [1, 0, 0]
4  const vector2 = [0, 1, 0]
5
6  // Act
7  const similarity = calculateCosineSimilarity(vector1, vector2)
8
9  // Assert
10  expect(similarity).toBe(0)
11})

Test Naming

typescript
1// ✅ GOOD: Descriptive test names
2test('returns empty array when no markets match query', () => { })
3test('throws error when OpenAI API key is missing', () => { })
4test('falls back to substring search when Redis unavailable', () => { })
5
6// ❌ BAD: Vague test names
7test('works', () => { })
8test('test search', () => { })

Code Smell Detection

Watch for these anti-patterns:

1. Long Functions

typescript
1// ❌ BAD: Function > 50 lines
2function processMarketData() {
3  // 100 lines of code
4}
5
6// ✅ GOOD: Split into smaller functions
7function processMarketData() {
8  const validated = validateData()
9  const transformed = transformData(validated)
10  return saveData(transformed)
11}

2. Deep Nesting

typescript
1// ❌ BAD: 5+ levels of nesting
2if (user) {
3  if (user.isAdmin) {
4    if (market) {
5      if (market.isActive) {
6        if (hasPermission) {
7          // Do something
8        }
9      }
10    }
11  }
12}
13
14// ✅ GOOD: Early returns
15if (!user) return
16if (!user.isAdmin) return
17if (!market) return
18if (!market.isActive) return
19if (!hasPermission) return
20
21// Do something

3. Magic Numbers

typescript
1// ❌ BAD: Unexplained numbers
2if (retryCount > 3) { }
3setTimeout(callback, 500)
4
5// ✅ GOOD: Named constants
6const MAX_RETRIES = 3
7const DEBOUNCE_DELAY_MS = 500
8
9if (retryCount > MAX_RETRIES) { }
10setTimeout(callback, DEBOUNCE_DELAY_MS)

Remember: Code quality is not negotiable. Clear, maintainable code enables rapid development and confident refactoring.