typescript-dev

This skill should be used when writing TypeScript, eliminating any types, implementing Zod validation, or when strict type safety is needed. Covers modern TS 5.5+ features and runtime validation patterns.

Jump to install

Repository: outfitter-dev/agents
Last source activity: January 27, 2026 at 15:45
Detected SKILL.md language: English
Stars: 28
Forks: 1

Install options

The review-first prompt is selected by default. You can switch to a direct command or download a local copy.

Install with Codex or Claude Copy this prompt, paste it into Codex, Claude, or another assistant, and let it review the skill page and install it for you.

A direct command skips the review prompt. Inspect the source before running it.

npx skills add https://github.com/outfitter-dev/agents --skill typescript-dev

The command stays on one line. Scroll horizontally to inspect it before copying.

Prefer a local copy? Download the files currently available to SkillsMP.

Review the source files

Read SKILL.md and any companion files shown by SkillsMP before deciding whether to install.

File Explorer

15 files

SKILL.md

Source instructions · Read-only preview

Back to search Back to installation

// ❌ NEVER
function process(data: any) { return data.value; }

// ✅ ALWAYS
function process(data: unknown): string {
  if (!hasValue(data)) throw new TypeError('Invalid');
  return data.value.toString();
}

function hasValue(v: unknown): v is { value: unknown } {
  return typeof v === 'object' && v !== null && 'value' in v;
}

async function fetchUser(id: string): Promise<User> {
  const data: unknown = await fetch(`/api/users/${id}`).then(r => r.json());
  return UserSchema.parse(data);
}

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

type UserError =
  | { readonly type: 'not-found'; readonly id: string }
  | { readonly type: 'network'; readonly message: string };

async function getUser(id: string): Promise<Result<User, UserError>> {
  try {
    const response = await fetch(`/api/users/${id}`);
    if (response.status === 404)
      return { ok: false, error: { type: 'not-found', id } };
    if (!response.ok)
      return { ok: false, error: { type: 'network', message: response.statusText } };
    return { ok: true, value: await response.json() };
  } catch (e) {
    return { ok: false, error: { type: 'network', message: String(e) } };
  }
}

// Caller must handle
const result = await getUser(id);
if (!result.ok) {
  switch (result.error.type) {
    case 'not-found': return showNotFound(result.error.id);
    case 'network': return showError(result.error.message);
  }
}
return renderUser(result.value);

// ❌ Allows { status: 'loading', data: user, error: 'Failed' }
type Request = { status: 'idle'|'loading'|'success'|'error'; data?: User; error?: string; };

// ✅ Only valid states
type RequestState =
  | { readonly status: 'idle' }
  | { readonly status: 'loading' }
  | { readonly status: 'success'; readonly data: User }
  | { readonly status: 'error'; readonly error: string };

function render(state: RequestState): JSX.Element {
  switch (state.status) {
    case 'idle': return <div>Ready</div>;
    case 'loading': return <div>Loading...</div>;
    case 'success': return <div>{state.data.name}</div>;
    case 'error': return <div>Error: {state.error}</div>;
    default: return assertNever(state);
  }
}

function assertNever(value: never): never {
  throw new Error(`Unhandled: ${JSON.stringify(value)}`);
}

declare const __brand: unique symbol;
type Brand<T, B extends string> = T & { readonly [__brand]: B };

type UserId = Brand<string, 'UserId'>;
type ProductId = Brand<string, 'ProductId'>;

function createUserId(value: string): UserId {
  if (!/^user-\d+$/.test(value)) throw new TypeError(`Invalid: ${value}`);
  return value as UserId;
}

const userId = createUserId('user-123');
// getUser(productId); // ❌ Type error
getUser(userId);       // ✅ Works

type SanitizedHtml = Brand<string, 'SanitizedHtml'>;

function sanitize(raw: string): SanitizedHtml {
  return escapeHtml(raw) as SanitizedHtml;
}

function render(html: SanitizedHtml): void {
  element.innerHTML = html; // Type proves sanitization
}

class DatabaseConnection implements Disposable {
  [Symbol.dispose]() { this.close(); }
}

function query() {
  using conn = new DatabaseConnection();
  return conn.query('SELECT * FROM users');
} // Automatically closed

async function asyncWork() {
  await using resource = new AsyncResource();
} // Disposed with await

const config = {
  port: 3000,
  host: 'localhost'
} satisfies Record<string, string | number>;

config.port // number (not string | number)

const routes = {
  home: '/',
  user: '/user/:id'
} as const satisfies Record<string, string>;

type HomeRoute = typeof routes.home; // '/'

function makeTuple<const T extends readonly unknown[]>(...args: T): T {
  return args;
}
const result = makeTuple('a', 'b', 'c'); // ['a', 'b', 'c'] not string[]

function isString(x: unknown) {
  return typeof x === 'string';
}
// Inferred: (x: unknown) => x is string

const strings = values.filter(isString); // string[]

type Route = `/${string}`;
type ApiRoute = `/api/v${number}/${string}`;

type ExtractParams<T extends string> =
  T extends `${string}:${infer P}/${infer R}` ? P | ExtractParams<`/${R}`>
  : T extends `${string}:${infer P}` ? P : never;

type Params = ExtractParams<'/user/:id/post/:postId'>; // 'id' | 'postId'

import { z } from 'zod';

const UserSchema = z.object({
  id: z.string().uuid(),
  email: z.string().email(),
  name: z.string().min(1).max(100)
});

type User = z.infer<typeof UserSchema>;

// safeParse preferred
const result = UserSchema.safeParse(data);
if (!result.success) {
  console.error(result.error.issues);
  return;
}
const user = result.data;

const ApiResponse = z.discriminatedUnion("type", [
  z.object({ type: z.literal("success"), data: z.unknown() }),
  z.object({ type: z.literal("error"), code: z.string(), message: z.string() })
]);

const EnvSchema = z.object({
  NODE_ENV: z.enum(['development', 'production', 'test']).default('development'),
  DATABASE_URL: z.string().url(),
  PORT: z.coerce.number().int().positive().default(3000)
});
const env = EnvSchema.parse(process.env);

import { zValidator } from '@hono/zod-validator';

app.post('/users', zValidator('json', UserSchema), (c) => {
  const user = c.req.valid('json');
  return c.json(user);
});

// User-defined
function isString(v: unknown): v is string {
  return typeof v === 'string';
}

// Assertion
function assertString(v: unknown): asserts v is string {
  if (typeof v !== 'string') throw new TypeError('Expected string');
}

// With noUncheckedIndexedAccess
const users: User[] = getUsers();
const first = users[0]; // User | undefined
if (first !== undefined) processUser(first);

/**
 * Authenticates user and returns session token.
 * @param credentials - User login credentials
 * @returns Session token valid for 24 hours
 * @throws {AuthenticationError} Invalid credentials
 * @example
 * const token = await authenticate({ email, password });
 */
export async function authenticate(credentials: Credentials): Promise<SessionToken>;

typescript-dev

Install options

Review the source files

TypeScript Development

TypeScript Development

Core Patterns

Modern TypeScript (5.2+)

Zod Validation

Type Guards

TSDoc

name	typescript-dev
description	This skill should be used when writing TypeScript, eliminating any types, implementing Zod validation, or when strict type safety is needed. Covers modern TS 5.5+ features and runtime validation patterns.
metadata	{"version":"1.0.0"}

typescript-dev

Source facts

Install options

Review the source files

More from this repository

TypeScript Development

TypeScript Development

Core Patterns

Modern TypeScript (5.2+)

Zod Validation

Type Guards

TSDoc

More from this repository