TypeScript/JavaScript Style Best Practices Skill

This skill enforces TypeScript strict mode, ESLint standards, and modern patterns for frontend development.

Core Standards

• Strict TypeScript: All strict flags enabled
• ESLint: Type-checked rules enabled
• No any: Use unknown or proper types
• Explicit returns: All functions typed

Naming Conventions

// Types/Interfaces: PascalCase
interface UserProfile { }

// Functions/variables: camelCase
function calculateTotal() { }
const userName = "john";

// Booleans: is/has/can/should prefix
const isLoading = true;
const hasPermission = false;

Type Definitions

// Prefer union types over enums
type Status = "pending" | "active" | "completed";

// Use as const for constant objects
const HttpStatus = {
  Ok: 200,
  NotFound: 404,
} as const;

// Discriminated unions
type Result<T> =
  | { success: true; data: T }
  | { success: false; error: Error };

React Patterns

// Typed props
interface ButtonProps {
  label: string;
  onClick: () => void;
  disabled?: boolean;
}

// Typed hooks
const [isOpen, setIsOpen] = useState(false);

// Typed event handlers
const handleSubmit = (e: React.FormEvent<HTMLFormElement>) => {};

Function Length Guidelines

• < 30 lines: Ideal
• 30-50 lines: Review for refactoring
• > 50 lines: Must be broken down

Anti-Patterns to Avoid

• Using any type
• Missing return types
• Using == instead of ===
• Unhandled promises
• Magic numbers/strings
• Vague variable/function names