coding-standards

name coding-standards description Baseline cross-project coding conventions for naming, readability, immutability, and code-quality review. Use detailed frontend or backend skills for framework-specific patterns. Use when reviewing code quality or naming with no framework-specific skill that applies. metadata {"origin":"ECC"} Coding Standards & Best Practices Baseline coding conventions applicable across projects. This skill is the shared floor, not the detailed framework playbook. Use frontend-patterns for React, state, forms, rendering, and UI architecture. Use backend-patterns or api-design for repository/service layers, endpoint design, validation, and server-specific concerns. Use rules/common/coding-style.md when you need the shortest reusable rule layer instead of a full skill walkthrough. When to Activate Starting a new project or module Reviewing code for quality and maintainability Refactoring existing code to follow conventions Enforcing naming, formatting, or structural consistency Setting up linting, formatting, or type-checking rules Onboarding new contributors to coding conventions Scope Boundaries Activate this skill for: descriptive naming immutability defaults readability, KISS, DRY, and YAGNI enforcement error-handling expectations and code-smell review Do not use this skill as the primary source for: React composition, hooks, or rendering patterns backend architecture, API design, or database layering domain-specific framework guidance when a narrower ECC skill already exists 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 // PASS: GOOD: Descriptive names const marketSearchQuery = 'election' const isUserAuthenticated = true const totalRevenue = 1000 // FAIL: BAD: Unclear names const q = 'election' const flag = true const x = 1000 Function Naming // PASS: GOOD: Verb-noun pattern async function fetchMarketData ( marketId : string ) { } function calculateSimilarity ( a : number [], b : number [] ) { } function isValidEmail ( email : string ): boolean { } // FAIL: BAD: Unclear or noun-only async function market ( id : string ) { } function similarity ( a, b ) { } function email ( e ) { } Immutability Pattern (CRITICAL) // PASS: ALWAYS use spread operator const updatedUser = { ...user, name : 'New Name' } const updatedArray = [...items, newItem] // FAIL: NEVER mutate directly user. name = 'New Name' // BAD items. push (newItem) // BAD Error Handling // PASS: 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' ) } } // FAIL: BAD: No error handling async function fetchData ( url ) { const response = await fetch (url) return response. json () } Async/Await Best Practices // PASS: GOOD: Parallel execution when possible const [users, markets, stats] = await Promise . all ([ fetchUsers (), fetchMarkets (), fetchStats () ]) // FAIL: BAD: Sequential when unnecessary const users = await fetchUsers () const markets = await fetchMarkets () const stats = await fetchStats () Type Safety // PASS: GOOD: Proper types interface Market { id : string name : string status : 'active' | 'resolved' | 'closed' created_at : Date } function getMarket ( id : string ): Promise < Market > { // Implementation } // FAIL: BAD: Using 'any' function getMarket ( id : any ): Promise < any > { // Implementation } React Best Practices Component Structure // PASS: 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 onClick = {onClick} disabled = {disabled} className = { ` btn btn- ${ variant }`} > {children} </ button > ) } // FAIL: BAD: No types, unclear structure export function Button ( props ) { return < button onClick = {props.onClick} > {props.children} </ button > } Custom Hooks // PASS: 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 // PASS: GOOD: Proper state updates const [count, setCount] = useState ( 0 ) // Functional update for state based on previous state setCount ( prev => prev + 1 ) // FAIL: BAD: Direct state reference setCount (count + 1 ) // Can be stale in async scenarios Conditional Rendering // PASS: GOOD: Clear conditional rendering {isLoading && < Spinner /> } {error && < ErrorMessage error = {error} /> } {data && < DataDisplay data = {data} /> } // FAIL: 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 // PASS: 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' // PASS: 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. issues }, { 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 // PASS: 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) // FAIL: 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' // PASS: GOOD: Memoize expensive computations // Copy before sorting - Array.prototype.sort mutates in place const sortedMarkets = useMemo ( () => { return [...markets]. sort ( ( a, b ) => b. volume - a. volume ) }, [markets]) // PASS: GOOD: Memoize callbacks const handleSearch = useCallback ( ( query : string ) => { setSearchQuery (query) }, []) Lazy Loading import { lazy, Suspense } from 'react' // PASS: GOOD: Lazy load heavy components const HeavyChart = lazy ( () => import ( './HeavyChart' )) export function Dashboard ( ) { return ( < Suspense fallback = { < Spinner /> }> < HeavyChart /> </ Suspense > ) } Database Queries // PASS: GOOD: Select only needed columns const { data } = await supabase . from ( 'markets' ) . select ( 'id, name, status' ) . limit ( 10 ) // FAIL: 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 // PASS: 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' , () => { }) // FAIL: BAD: Vague test names test ( 'works' , () => { }) test ( 'test search' , () => { }) Code Smell Detection Watch for these anti-patterns: 1. Long Functions // FAIL: BAD: Function > 50 lines function processMarketData ( ) { // 100 lines of code } // PASS: GOOD: Split into smaller functions function processMarketData ( ) { const validated = validateData () const transformed = transformData (validated) return saveData (transformed) } 2. Deep Nesting // FAIL: BAD: 5+ levels of nesting if (user) { if (user. isAdmin ) { if (market) { if (market. isActive ) { if (hasPermission) { // Do something } } } } } // PASS: GOOD: Early returns if (!user) return