coding-standards

name: coding-standards description: Universal coding standards, best practices, and patterns for TypeScript, JavaScript, React, and Node.js development.

Coding Standards & Best Practices

Universal coding standards applicable across all projects.

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

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;

Fluent Naming

// ✅ GOOD: Fluent naming
private readonly searchCustomers = inject(SearchCustomersUseCase);

public searchCustomersBy(filters: SearchFilters) {
  return this.searchCustomers.by(filters); // ✅ GOOD - fluent
}

// ❌ BAD: Unclear names
public searchCustomers(searchFilters: SearchFilters) {
  return this.searchCustomers.search(searchFilters); // ❌ BAD - can't read it as fluent
}

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
}

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

File Organization

Project Structure

See Codemaps in DOCS/CODEMAPS

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.