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typescript

typescript

github.com/gentleman-programmingDevelopment661496 installsUpdated 31w ago
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About typescript

A TypeScript coding-guidance skill for developers, covering type definitions, interface design, and type safety patterns for writing or reviewing code.

Key features

  1. 01Derive union types from const objects
  2. 02Keep interfaces flat
  3. 03Avoid using any
  4. 04Use utility types and generics
  5. 05Apply type guards and type imports

Use cases

  1. 01Define literal types for statuses
  2. 02Design user data structures
  3. 03Parse and validate unknown input

Install

Copy the command and run it in a terminal.

$npx skills add https://github.com/gentleman-programming/gentleman-skills --skill typescript

After installing, type/typescriptin Claude Code to confirm it loaded.

Details

From the project README

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];
}

// ❌ NEVER
function parse(input: any): any { }

Utility Types

Pick<User, "id" | "name">     // Select fields
Omit<User, "id">              // Exclude fields
Partial<User>                 // All optional
Required<User>                // All required
Readonly<User>                // All readonly
Record<string, User>          // Object type
Extract<Union, "a" | "b">     // Extract from union
Exclude<Union, "a">           // Exclude from union
NonNullable<T | null>         // Remove null/undefined
ReturnType<typeof fn>         // Function return type
Parameters<typeof fn>         // Function params tuple

Type Guards

function isUser(value: unknown): value is User {
  return (
    typeof value === "object" &&
    value !== null &&
    "id" in value &&
    "name" in value
  );
}

Import Types

import type { User } from "./types";
import { createUser, type Config } from "./utils";

Keywords

typescript, ts, types, interfaces, generics, strict mode, utility types

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