coding-standards

Coding Standards Skill

Enforce consistent code quality principles and patterns across all implementation work.

When to Activate

• During any code implementation task (/cdf:implement)
• When reviewing or refactoring code
• When writing new functions, classes, or modules
• When the user requests coding guidance or best practices

---

Pattern Index

Core Principles

Principle	Rule
Readability First	Optimize for human understanding over cleverness
KISS	Simplest solution that works is usually best
DRY	Extract repeated logic, avoid premature abstraction
YAGNI	Don't build for hypothetical future requirements

Readability First

// BAD: Clever but unclear
const r = a.filter(x => x.t === 'p' && x.s > 0).map(x => x.v);

// GOOD: Clear and intentional
const activeProducts = items
  .filter(item => item.type === 'product' && item.stock > 0)
  .map(item => item.value);

KISS (Keep It Simple, Stupid)

// BAD: Over-engineered
class UserNameFormatter {
  private strategies = new Map<string, FormatterStrategy>();
  constructor() {
    this.registerStrategy('default', new DefaultStrategy());
    // ... 50 more lines
  }
}

// GOOD: Simple function
function formatUserName(user: User): string {
  return `${user.firstName} ${user.lastName}`.trim();
}

DRY (Don't Repeat Yourself)

// BAD: Duplicated logic
function validateEmail(email: string) {
  return email.includes('@') && email.includes('.');
}
function validateUserEmail(user: User) {
  return user.email.includes('@') && user.email.includes('.');
}

// GOOD: Single source of truth
function isValidEmail(email: string): boolean {
  return email.includes('@') && email.includes('.');
}
function validateUserEmail(user: User): boolean {
  return isValidEmail(user.email);
}

YAGNI (You Aren't Gonna Need It)

// BAD: Building for imaginary requirements
interface User {
  id: string;
  name: string;
  futureField1?: string;  // "We might need this"
  extensionData?: Record<string, unknown>;  // "For flexibility"
}

// GOOD: Build what you need now
interface User {
  id: string;
  name: string;
}