Modules, Runtime & Tooling

Publishing Packages

Publishing a JS/TS package means defining runtime entrypoints, type entrypoints, dependency boundaries, exports, files, versioning, compatibility, and consumer expectations.

Package exports define the public surface
Declarations must match emitted JavaScript
Peer dependencies express host-provided packages
Files should be intentionally published
Semver is a communication tool

ESM package entrypoint

{
  "name": "@acme/utils",
  "version": "1.0.0",
  "type": "module",
  "exports": {
    ".": {
      "types": "./dist/index.d.ts",
      "import": "./dist/index.js"
    }
  },
  "files": ["dist"]
}

The package declares both runtime and type entrypoints.

Publishing checklist
Concern	Question
Entrypoints	What can consumers import?
Types	Do declarations match emitted JS?
Dependencies	Which packages are runtime, dev, peer?
Files	What actually gets published?
Module format	ESM, CJS, or both?
Versioning	Is this change breaking?
Consumer tests	Did a real consuming project import it?