Breaking TypeScript NPM package into multiple files without exposing internal components

Question

I have an NPM package written in TypeScript which is designd to work with Node.js applications. I have classes in this package which have methods that are internal use only, although I cannot mark them as private because they are used by other components within the package. To solve this problem, I do not export the class from the project, and when I return an instance of the class to the caller, I type cast it as an interface which only has the publicly accessible methods.

This works fine, but if I want to break my project into smaller files, how can I do this without being forced to export my classes, and risk the misuse of my NPM module?

Here is a simplified example of what I am trying to do:

File: internal.ts

// Can I make this class not publicly accessible?
export class InternalClass {
    constructor() {

    }

    public sharedMethod(): void {
        // Accessible to users of the package
    }

    public protectedMethod(): void {
        // Only for use within the package
    }
}

File: external.ts

import { InternalClass } from "./internal";

export interface ExternalInterface {
    sharedMethod(): void;
    // protectedMethod is not available outside the package
}

export function makeInterface(): ExternalInterface {
    return new InternalClass();
}

Any ideas for how to do this well would be greatly appreciated.

Answer 1

The way I do this is by controlling what exactly gets exposed by the npm package.

For example if my package.json looks like this:

{
  ....
  "main": "dist/index.js",
  "typings": "typings/index.d.ts",
  ....
}

then in the corresponding index.ts I can manually control what will be exposed (exported) as part of the package.

export * from "./lib/Helper";
export * from "./lib/Log";

import * as M from "./lib/Maps";
export {M as Maps};

If I have module/class that I do not want to be accessible "outside" - I simply do not export it as part of index.ts or its referenced children. This does not prohibit me though to import and use it internally in the same package.