kursku 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
// ✅ GOOD: Descriptive names
const marketSearchQuery = 'election'
const isUserAuthenticated = true
const totalRevenue = 1000
// ❌ BAD: Unclear names
const q = 'election'
const flag = true
const x = 1000
Function Naming
// ✅ GOOD: Verb-noun pattern
async function fetchMarketData(marketId: string) { }
function calculateSimilarity(a: number[], b: number[]) { }
function isValidEmail(email: string): boolean { }
// ❌ BAD: Unclear or noun-only
async function market(id: string) { }
function similarity(a, b) { }
function email(e) { }
Immutability Pattern (CRITICAL)
// ✅ ALWAYS use spread operator
const updatedUser = {
...user,
name: 'New Name'
}
const updatedArray = [...items, newItem]
// ❌ NEVER mutate directly
user.name = 'New Name' // BAD
items.push(newItem) // BAD
Error Handling
// ✅ GOOD: Comprehensive error handling
async function fetchData(url: string) {
try {
const response = await fetch(url)
if (!response.ok) {
throw new Error(`HTTP ${response.status}: ${response.statusText}`)
}
return await response.json()
} catch (error) {
console.error('Fetch failed:', error)
throw new Error('Failed to fetch data')
}
}
// ❌ BAD: No error handling
async function fetchData(url) {
const response = await fetch(url)
return response.json()
}
Async/Await Best Practices
// ✅ GOOD: Parallel execution when possible
const [users, markets, stats] = await Promise.all([
fetchUsers(),
fetchMarkets(),
fetchStats()
])
// ❌ BAD: Sequential when unnecessary
const users = await fetchUsers()
const markets = await fetchMarkets()
const stats = await fetchStats()
Type Safety
// ✅ GOOD: Proper types
interface Market {
id: string
name: string
status: 'active' | 'resolved' | 'closed'
created_at: Date
}
function getMarket(id: string): Promise<Market> {
// Implementation
}
// ❌ BAD: Using 'any'
function getMarket(id: any): Promise<any> {
// Implementation
}
React Best Practices
Component Structure
// ✅ GOOD: Functional component with types
interface ButtonProps {
children: React.ReactNode
onClick: () => void
disabled?: boolean
variant?: 'primary' | 'secondary'
}
export function Button({
children,
onClick,
disabled = false,
variant = 'primary'
}: ButtonProps) {
return (
<button
disabled={disabled}
className={`btn btn-${variant}`}
>
{children}
</button>
)
}
// ❌ BAD: No types, unclear structure
export function Button(props) {
return <button
}
Custom Hooks
// ✅ GOOD: Reusable custom hook
export function useDebounce<T>(value: T, delay: number): T {
const [debouncedValue, setDebouncedValue] = useState<T>(value)
useEffect(() => {
const handler = setTimeout(() => {
setDebouncedValue(value)
}, delay)
return () => clearTimeout(handler)
}, [value, delay])
return debouncedValue
}
// Usage
const debouncedQuery = useDebounce(searchQuery, 500)
State Management
// ✅ GOOD: Proper state updates
const [count, setCount] = useState(0)
// Functional update for state based on previous state
setCount(prev => prev + 1)
// ❌ BAD: Direct state reference
setCount(count + 1) // Can be stale in async scenarios
Conditional Rendering
// ✅ GOOD: Clear conditional rendering
{isLoading && <Spinner />}
{error && <ErrorMessage error={error} />}
{data && <DataDisplay data={data} />}
// ❌ BAD: Ternary hell
{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
// ✅ GOOD: Consistent response structure
interface ApiResponse<T> {
success: boolean
data?: T
error?: string
meta?: {
total: number
page: number
limit: number
}
}
// Success response
return NextResponse.json({
success: true,
data: markets,
meta: { total: 100, page: 1, limit: 10 }
})
// Error response
return NextResponse.json({
success: false,
error: 'Invalid request'
}, { status: 400 })
Input Validation
import { z } from 'zod'
// ✅ GOOD: Schema validation
const CreateMarketSchema = z.object({
name: z.string().min(1).max(200),
description: z.string().min(1).max(2000),
endDate: z.string().datetime(),
categories: z.array(z.string()).min(1)
})
export async function POST(request: Request) {
const body = await request.json()
try {
const validated = CreateMarketSchema.parse(body)
// Proceed with validated data
} catch (error) {
if (error instanceof z.ZodError) {
return NextResponse.json({
success: false,
error: 'Validation failed',
details: error.errors
}, { status: 400 })
}
}
}
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
// ✅ GOOD: Explain WHY, not WHAT
// Use exponential backoff to avoid overwhelming the API during outages
const delay = Math.min(1000 * Math.pow(2, retryCount), 30000)
// Deliberately using mutation here for performance with large arrays
items.push(newItem)
// ❌ BAD: Stating the obvious
// Increment counter by 1
count++
// Set name to user's name
name = user.name
JSDoc for Public APIs
/**
* Searches markets using semantic similarity.
*
* @param query - Natural language search query
* @param limit - Maximum number of results (default: 10)
* @returns Array of markets sorted by similarity score
* @throws {Error} If OpenAI API fails or Redis unavailable
*
* @example
* ```typescript
* const results = await searchMarkets('election', 5)
* console.log(results[0].name) // "Trump vs Biden"
* ```
*/
export async function searchMarkets(
query: string,
limit: number = 10
): Promise<Market[]> {
// Implementation
}
Performance Best Practices
Memoization
import { useMemo, useCallback } from 'react'
// ✅ GOOD: Memoize expensive computations
const sortedMarkets = useMemo(() => {
return markets.sort((a, b) => b.volume - a.volume)
}, [markets])
// ✅ GOOD: Memoize callbacks
const handleSearch = useCallback((query: string) => {
setSearchQuery(query)
}, [])
Lazy Loading
import { lazy, Suspense } from 'react'
// ✅ GOOD: Lazy load heavy components
const HeavyChart = lazy(() => import('./HeavyChart'))
export function Dashboard() {
return (
<Suspense fallback={<Spinner />}>
<HeavyChart />
</Suspense>
)
}
Database Queries
// ✅ GOOD: Select only needed columns
const { data } = await supabase
.from('markets')
.select('id, name, status')
.limit(10)
// ❌ BAD: Select everything
const { data } = await supabase
.from('markets')
.select('*')
Testing Standards
Test Structure (AAA Pattern)
test('calculates similarity correctly', () => {
// Arrange
const vector1 = [1, 0, 0]
const vector2 = [0, 1, 0]
// Act
const similarity = calculateCosineSimilarity(vector1, vector2)
// Assert
expect(similarity).toBe(0)
})
Test Naming
// ✅ GOOD: Descriptive test names
test('returns empty array when no markets match query', () => { })
test('throws error when OpenAI API key is missing', () => { })
test('falls back to substring search when Redis unavailable', () => { })
// ❌ BAD: Vague test names
test('works', () => { })
test('test search', () => { })
Code Smell Detection
Watch for these anti-patterns:
1. Long Functions
// ❌ BAD: Function > 50 lines
function processMarketData() {
// 100 lines of code
}
// ✅ GOOD: Split into smaller functions
function processMarketData() {
const validated = validateData()
const transformed = transformData(validated)
return saveData(transformed)
}
2. Deep Nesting
// ❌ BAD: 5+ levels of nesting
if (user) {
if (user.isAdmin) {
if (market) {
if (market.isActive) {
if (hasPermission) {
// Do something
}
}
}
}
}
// ✅ GOOD: Early returns
if (!user) return
if (!user.isAdmin) return
if (!market) return
if (!market.isActive) return
if (!hasPermission) return
// Do something
3. Magic Numbers
// ❌ BAD: Unexplained numbers
if (retryCount > 3) { }
setTimeout(callback, 500)
// ✅ GOOD: Named constants
const MAX_RETRIES = 3
const DEBOUNCE_DELAY_MS = 500
if (retryCount > MAX_RETRIES) { }
setTimeout(callback, DEBOUNCE_DELAY_MS)
Remember: Code quality is not negotiable. Clear, maintainable code enables rapid development and confident refactoring.
When to Use
This skill is applicable to execute the workflow or actions described in the overview.