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.

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