TypeScript Library Development

Quick Start

// package.json
{
  "name": "my-library",
  "version": "1.0.0",
  "type": "module",
  "main": "./dist/index.cjs",
  "module": "./dist/index.js",
  "types": "./dist/index.d.ts",
  "exports": {
    ".": {
      "import": { "types": "./dist/index.d.ts", "default": "./dist/index.js" },
      "require": { "types": "./dist/index.d.cts", "default": "./dist/index.cjs" }
    }
  },
  "files": ["dist"]
}

tsconfig.json Essentials

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "declaration": true,
    "declarationMap": true,
    "sourceMap": true,
    "outDir": "dist",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true
  },
  "include": ["src"],
  "exclude": ["**/*.test.ts"]
}

Key Practices

• Exports field: Required for proper ESM/CJS dual support
• Types first: In conditional exports, types must come before default
• Files array: Only publish what's needed (dist, README, LICENSE)
• Declaration maps: Enable go-to-definition in consuming projects
• Peer dependencies: For frameworks/libraries users must also install

Publishing Checklist

1. Update version in package.json
2. Build: npm run build
3. Test the package: npm pack and inspect tarball
4. Publish: npm publish (or npm publish --access public for scoped)

Common Tools

• tsup: Zero-config bundler for TypeScript libraries
• unbuild: Build system with automatic CJS/ESM
• changesets: Version management and changelogs

Reference Files

• references/tsconfig.md - tsconfig options explained
• references/exports.md - Package exports patterns
• references/publishing.md - npm publishing workflow