ts-library

SKILL.md

TypeScript Library Development

Patterns for authoring high-quality TypeScript libraries, extracted from studying unocss, shiki, unplugin, vite, vitest, vueuse, zod, trpc, drizzle-orm, and more.

When to Use

Starting a new TypeScript library (single or monorepo)

Setting up package.json exports for dual CJS/ESM

Configuring tsconfig for library development

Choosing build tools (tsdown, unbuild)

Designing type-safe APIs (builder, factory, plugin patterns)

Writing advanced TypeScript types

Setting up vitest for library testing

Configuring release workflow and CI

For Nuxt module development: use nuxt-modules skill

Quick Reference

Working on...
Load file

New project setup
references/project-setup.md

Package exports
references/package-exports.md

tsconfig options
references/typescript-config.md

Build configuration
references/build-tooling.md

ESLint config
references/eslint-config.md

API design patterns
references/api-design.md

Type inference tricks
references/type-patterns.md

Testing setup
references/testing.md

Release workflow
references/release.md

CI/CD setup
references/ci-workflows.md

Loading Files

Consider loading these reference files based on your task:

 references/project-setup.md - if starting a new TypeScript library project

 references/package-exports.md - if configuring package.json exports or dual CJS/ESM

 references/typescript-config.md - if setting up or modifying tsconfig.json

 references/build-tooling.md - if configuring tsdown, unbuild, or build scripts

 references/eslint-config.md - if setting up ESLint for library development

 references/api-design.md - if designing public APIs, builder patterns, or plugin systems

 references/type-patterns.md - if working with advanced TypeScript types or type inference

 references/testing.md - if setting up vitest or writing tests for library code

 references/release.md - if configuring release workflow or versioning

 references/ci-workflows.md - if setting up GitHub Actions or CI/CD pipelines

DO NOT load all files at once. Load only what's relevant to your current task.

New Library Workflow

Create project structure → load references/project-setup.md

Configure package.json exports → load references/package-exports.md

Set up build with tsdown → load references/build-tooling.md

Verify build: pnpm build && pnpm pack --dry-run — check output includes .mjs, .cjs, .d.ts

Add tests → load references/testing.md

Configure release → load references/release.md

Quick Start

// package.json (minimal)
{
  "name": "my-lib",
  "type": "module",
  "exports": {
    ".": {
      "import": "./dist/index.mjs",
      "require": "./dist/index.cjs"
    }
  },
  "main": "./dist/index.cjs",
  "module": "./dist/index.mjs",
  "types": "./dist/index.d.ts",
  "files": ["dist"]
}

// tsdown.config.ts
import { defineConfig } from 'tsdown'

export default defineConfig({
  entry: ['src/index.ts'],
  format: ['esm', 'cjs'],
  dts: true,
})

Key Principles

ESM-first: "type": "module" with .mjs outputs

Dual format: always support both CJS and ESM consumers

moduleResolution: "Bundler" for modern TypeScript

tsdown for most builds, unbuild for complex cases

Smart defaults: detect environment, don't force config

Tree-shakeable: lazy getters, proper sideEffects: false

Token efficiency: Main skill ~300 tokens, each reference ~800-1200 tokens