ts-library

This skill provides a structured framework for building maintainable, high-performance TypeScript libraries. It synthesizes architectural standards observed in modern ecosystems like Vite, Vitest, and Zod. Instead of manually configuring complex build chains, you get a standardized approach to dual-format packaging (CJS and ESM) and precise TypeScript configuration. The skill enforces ESM-first principles while ensuring legacy compatibility, tree-shakable output, and type-safe API patterns. It prioritizes build speed and developer ergonomics by advocating for tools like tsdown and unbuild over manual Babel or Rollup configurations. By focusing on modern resolution strategies and standardized export conditions, this skill helps authors ship packages that work reliably across diverse runtime environments, from Node.js to edge computing, without common pitfalls like missing types or broken import conditions.

When to Use This Skill

• •Developing a utility library intended for both browser and Node.js environments
• •Refactoring an existing project to support modern module systems
• •Setting up a release pipeline for a new open-source TypeScript package
• •Designing type-safe builder patterns for public-facing SDKs

How to Invoke This Skill

Example prompts that trigger this skill in Claude Code, Cursor, or Antigravity:

• “How should I structure my TypeScript library for dual-format output?
• “Configure my library to support both ESM and CJS correctly
• “What is the best build tool for a modern TypeScript package?
• “Help me set up tree-shaking for my TS project
• “How to handle exports in package.json for a TypeScript library?

Pro Tips

• 💡Combine this skill with 'documentation-generation' to ensure your well-designed APIs are clearly documented for consumers.
• 💡For complex API design challenges, iterate with the skill, asking for examples for different patterns (e.g., 'show me a factory pattern example for a plugin API').
• 💡When troubleshooting build issues, use the skill to compare your `tsconfig` and build tool configurations against recommended best practices from popular libraries.

What this skill does

• •Configuring package.json for dual ESM and CJS compatibility
• •Optimizing tsconfig.json for modern bundler resolution
• •Selecting appropriate build pipelines using tsdown or unbuild
• •Implementing tree-shakable API architectures
• •Automating library test suites with Vitest

When not to use it

• ✕Developing specialized Nuxt modules (use the nuxt-modules skill instead)
• ✕Small, single-file scripts that do not require packaging or distribution

Example workflow

1. Initialize project structure following ESM-first principles
2. Configure tsconfig.json with Bundler module resolution
3. Define package.json exports to handle CJS and ESM consumers
4. Select and configure a build tool like tsdown or unbuild
5. Write and run unit tests using Vitest
6. Implement automated release workflows for npm publishing

Prerequisites

• –Familiarity with standard TypeScript syntax
• –Basic understanding of npm/yarn/pnpm package management

Pitfalls & limitations

• !Ignoring the impact of sideEffects: false on code tree-shaking
• !Using outdated module resolutions that break modern bundlers
• !Forgetting to include declaration files in package exports

FAQ

How it compares

This skill replaces fragmented, outdated blog post advice with validated, consistent patterns derived from current industry-leading libraries.

Source & trust

Recommended Rules

Recommended Workflows

Recommended MCP Servers