coding-standards

name	coding-standards
description	Universal coding standards - naming, formatting, error handling, immutability, SOLID principles

Coding Standards

Naming Conventions

Tip	Format	Ornek
Variable	camelCase	userName, itemCount
Function	camelCase, verb-first	getUserById, calculateTotal
Class/Type	PascalCase	UserService, OrderItem
Constant	UPPER_SNAKE	MAX_RETRIES, API_URL
File	kebab-case	user-service.ts, order-item.ts
Boolean	is/has/should prefix	isActive, hasPermission

Immutability

// YANLIS: Mutate
user.name = newName;
items.push(newItem);

// DOGRU: Yeni obje
const updated = { ...user, name: newName };
const newItems = [...items, newItem];

Error Handling

// Custom error class
class AppError extends Error {
  constructor(public code: string, message: string, public statusCode = 500) {
    super(message);
  }
}

// Try-catch with specific errors
try {
  const result = await riskyOperation();
  return result;
} catch (error) {
  if (error instanceof ValidationError) {
    throw new AppError('VALIDATION', error.message, 400);
  }
  throw new AppError('INTERNAL', 'Unexpected error', 500);
}

Function Rules

• Max 50 satir, tek sorumluluk
• Max 3 parametre (fazlasi obje olarak)
• Early return (nested if yerine guard clause)
• Pure function tercih et (side effect yok)

// YANLIS: Deep nesting
function process(user) {
  if (user) {
    if (user.isActive) {
      if (user.hasPermission) {
        return doWork(user);
      }
    }
  }
}

// DOGRU: Early return
function process(user) {
  if (!user) return null;
  if (!user.isActive) return null;
  if (!user.hasPermission) return null;
  return doWork(user);
}

SOLID Principles

Prensip	Kural
S - Single Responsibility	Her sinif/fonksiyon tek is
O - Open/Closed	Extension'a acik, modification'a kapali
L - Liskov Substitution	Alt tip, ust tipin yerine gecebilmeli
I - Interface Segregation	Kucuk, specific interface'ler
D - Dependency Inversion	Abstraction'a baglan, concrete'e degil

Result<T,E> Pattern (Functional Error Handling)

Exception fırlatmak yerine explicit error dondur. Ozellikle API katmaninda, service'lerde ve veri islemede kullan.

// Result type tanimi
type Result<T, E = Error> =
  | { ok: true; value: T }
  | { ok: false; error: E };

// Kullanim
function parseConfig(raw: string): Result<Config, ValidationError> {
  try {
    const parsed = JSON.parse(raw);
    if (!isValidConfig(parsed)) {
      return { ok: false, error: new ValidationError('Invalid config shape') };
    }
    return { ok: true, value: parsed as Config };
  } catch {
    return { ok: false, error: new ValidationError('Invalid JSON') };
  }
}

// Tuketim
const result = parseConfig(input);
if (!result.ok) {
  logger.warn('Config parse failed', { error: result.error.message });
  return fallbackConfig;
}
const config = result.value;

Ne zaman kullan: Service layer, parser, validator, external API cagrisi Ne zaman kullanma: Basit utility, internal fonksiyon (try/catch yeterli)

Comment Rules

• Yorumlar zamansiz olmali: "Simdi boyle cunku..." yerine "Bu yaklasim X sebebiyle tercih edildi" yaz
• Neden > Ne: Kod ne yaptigini zaten gosteriyor, NEDEN yaptigini yaz
• Clarity over brevity: Kisa yorum ama anlamsizsa, uzun ama anlamli yorum yaz
• Yanlis yorum > yorum yok: Yanlis yorum tehlikelidir, guncellenmeyen yorum sil

// YANLIS: Ne yaptigini anlatiyor (gereksiz)
// Kullanici adini buyuk harfe cevir
const name = user.name.toUpperCase();

// DOGRU: Neden yapildigini anlatiyor
// Legacy API buyuk harf bekliyor, v3'te kaldirilacak
const name = user.name.toUpperCase();

function vs Arrow Function

Durum	Tercih	Neden
Exported fonksiyon	function declaration	Hoisted, debug stack trace'de gorunur
React component	function declaration	Tutarlilik, DevTools'da isim gorunur
Callback, inline	Arrow =>	Kisa, this binding yok
Method	Arrow (class field)	this binding garantili

// DOGRU: Exported fonksiyon
export function calculateTotal(items: Item[]): number {
  return items.reduce((sum, item) => sum + item.price, 0);
}

// DOGRU: Callback
const filtered = items.filter(item => item.active);

Anti-Patterns

Anti-Pattern	Cozum
Magic number	Named constant kullan
God class/function	Parcala, tek sorumluluk
console.log debug	Logger kullan, commit etme
Hardcoded values	Config/env variable
Any type	Specific type tanimla