TypeScript Academy · Lesson

Publishing a Type Utility Library

Package and share custom utility types on npm.

What Is a Type Utility Library?

A type utility library exports only TypeScript types — no runtime code. Popular examples include type-fest, ts-essentials, and utility-types.

// A type utility library exports types like:
export type DeepPartial<T> = T extends object
  ? { [K in keyof T]?: DeepPartial<T[K]> }
  : T;

Keep it simple: a single src/index.ts that re-exports all utilities, with tsconfig.json configured to emit declarations only.

// tsconfig.json
{
  "compilerOptions": {
    "declaration": true,
    "emitDeclarationOnly": true,
    "outDir": "dist",
    "strict": true
  }
}