Typescript

This is a strict TypeScript style guide that enforces two main patterns: const objects with type extraction instead of string unions, and flat interfaces with no inline nesting. It's opinionated about banning `any` entirely in favor of `unknown` and generics. The const types pattern is clever because you get both runtime values and type safety from a single source, which genuinely makes refactoring easier. The flat interface rule might feel restrictive if you're used to inline objects, but it does force cleaner separation. Also includes a solid reference for utility types and type guards. Use this if you want strict conventions on a team or you're tired of inconsistent TypeScript across a codebase.

skills.sh installs: 500
GitHub stars: 665
last updated: Aug 21, 2026

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Install

$ npx -y skills add gentleman-programming/gentleman-skills --skill typescript --agent claude-code

Installs into .claude/skills of the current project.

Files

Const Types Pattern (REQUIRED)

// ✅ ALWAYS: Create const object first, then extract type
const STATUS = {
  ACTIVE: "active",
  INACTIVE: "inactive",
  PENDING: "pending",
} as const;

type Status = (typeof STATUS)[keyof typeof STATUS];

// ❌ NEVER: Direct union types
type Status = "active" | "inactive" | "pending";

Why? Single source of truth, runtime values, autocomplete, easier refactoring.

Flat Interfaces (REQUIRED)

// ✅ ALWAYS: One level depth, nested objects → dedicated interface
interface UserAddress {
  street: string;
  city: string;
}

interface User {
  id: string;
  name: string;
  address: UserAddress;  // Reference, not inline
}

interface Admin extends User {
  permissions: string[];
}

// ❌ NEVER: Inline nested objects
interface User {
  address: { street: string; city: string };  // NO!
}

Never Use `any`

// ✅ Use unknown for truly unknown types
function parse(input: unknown): User {
  if (isUser(input)) return input;
  throw new Error("Invalid input");
}

// ✅ Use generics for flexible types
function first<T>(arr: T[]): T | undefined {
  return arr[0];
}

SKILL.md on GitHub