How to split a typescript package into multiple submodules?

Question

My newest typescript project is split into different modules and submodules.

My file structure:

package.json
(...)
/src
| /module1
| | index.ts
| | (...)
| | /subModule1
| | | index.ts
| | | (...)
| | /subModule2
|   | index.ts
|   | (...)
| /module2
  | index.ts
  | (...)

Every (sub)module has a index.ts file holding the module's exports.

Now I finally want to publish my package. One should be able to import stuff from the modules in the following way:

import { A } from "package/module1";
import { B, C } from "package/module1/subModule2";

I've already used this syntax on importing stuff from other packages on npm. But I can't find any explanations on how to implement such behavior. I've found some article explaining it for multiple files, but not for multiple modules structured in folders and subfolders.

Answer 1

See "Subpath exports" in Node documentation:

• https://nodejs.org/api/packages.html#subpath-exports

Example:

{
  "main": "./main.js",
  "exports": {
    ".": "./main.js",
    "./submodule": "./src/submodule.js"
  }
}

This article may help you with that:

• Node.JS (New) Package.json Exports Field by Thomas Juster

Plus some TypeScript-specific info in this issue on GitHub:

• Support for NodeJS 12.7+ package exports #33079

And since you say that you've already used this syntax on importing stuff from other packages on npm, then you might also take a look at the source code of those packages to see how they do it.