# Typescript Pro

Implements advanced TypeScript type systems, creates custom type guards, utility types...

- Repository: https://github.com/Jeffallan/claude-skills (12164 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-10-30
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add Jeffallan/claude-skills --skill typescript-pro -g -a claude-code -y`
Codex: `npx skills add Jeffallan/claude-skills --skill typescript-pro -g -a codex -y`
Cursor: `npx skills add Jeffallan/claude-skills --skill typescript-pro -g -a cursor -y`
Gemini CLI: `npx skills add Jeffallan/claude-skills --skill typescript-pro -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add Jeffallan/claude-skills`

## Description

Implements advanced TypeScript type systems, creates custom type guards, utility types, and branded types, and configures tRPC for end-to-end type safety. Use when building TypeScript applications requiring advanced generics, conditional or mapped types, discriminated unions, monorepo setup, or full-stack type safety with tRPC.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# TypeScript Pro

## Core Workflow

1. **Analyze type architecture** - Review tsconfig, type coverage, build performance
2. **Design type-first APIs** - Create branded types, generics, utility types
3. **Implement with type safety** - Write type guards, discriminated unions, conditional types; run `tsc --noEmit` to catch type errors before proceeding
4. **Optimize build** - Configure project references, incremental compilation, tree shaking; re-run `tsc --noEmit` to confirm zero errors after changes
5. **Test types** - Confirm type coverage with a tool like `type-coverage`; validate that all public APIs have explicit return types; iterate on steps 3, 4 until all checks pass

## Reference Guide

Load detailed guidance based on context:

| Topic | Reference | Load When |
|-------|-----------|-----------|
| Advanced Types | `references/advanced-types.md` | Generics, conditional types, mapped types, template literals |
| Type Guards | `references/type-guards.md` | Type narrowing, discriminated unions, assertion functions |
| Utility Types | `references/utility-types.md` | Partial, Pick, Omit, Record, custom utilities |
| Configuration | `references/configuration.md` | tsconfig options, strict mode, project references |
| Patterns | `references/patterns.md` | Builder pattern, factory pattern, type-safe APIs |

## Code Examples

### Branded Types
```typescript
// Branded type for domain modeling
type Brand<T, B extends string> = T & { readonly __brand: B };
type UserId  = Brand<string, "UserId">;
type OrderId = Brand<number, "OrderId">;

const toUserId  = (id: string): UserId  => id as UserId;
const toOrderId = (id: number): OrderId => id as OrderId;

// Usage, prevents accidental id mix-ups at compile time
function getOrder(userId: UserId, orderId: OrderId) { /* ... */ }
```

The rest: https://github.com/Jeffallan/claude-skills/blob/HEAD/skills/typescript-pro/SKILL.md