TypeScript Library Development

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

nuxt-modules

Quick Reference

Loading Files

• 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

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