I am writing a JavaScript library that I would like to be importable via script tag, ES6 imports, and traditional (Node) requires, with or without TypeScript or any build systems. I am finding this all bafflingly difficult.

In my package.json file, I have defined the following exports (simplifying to only relevant exports):

"exports": {
    ".": {
        "require": "./dist/slim.copper.cjs",
        "import": "./dist/slim.copper.js",
        "types": "./dist/typed.copper.d.ts"
    },
}

In a test TypeScript project, I import my library like this: import Copper from "@jwrunge/copper";

Type hints and intellisense work great, and I can compile the code to JavaScript without error. However, when I run the JS code with Node, I get this error:

C:UsersjrungeDocumentsCODEcopper_testsrcindex.js:3
var copper_1 = require("@jwrunge/copper");
               ^

Instead change the require of slim.copper.js in C:UsersjrungeDocumentsCODEcopper_testsrcindex.js to a dynamic import() which is available in all CommonJS modules.
    at Object.<anonymous> (C:UsersjrungeDocumentsCODEcopper_testsrcindex.js:3:16) {
  code: 'ERR_REQUIRE_ESM'
}

The JavaScript output from TypeScript is still appropriately typed, but interestingly uses require:

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var copper_1 = require("@jwrunge/copper");
var store1 = copper_1.default.store("foo", { value: 12 });

Interestingly, when I console.log copper_1 in the JS output and comment out all other code, I get this:

{
  store: [Function: store],
  ustore: [Function: ustore],
  getFunc: [Function: getFunc],
  addFuncs: [Function: addFuncs],
  config: [Function: config]
}

where default does not exist on the imported copper_1 and instead appears to be a direct import of the .cjs file (as I would expect from the use of require).

1. Is that what’s happening? The JS output is using the .cjs version of the library, which does not (like the .js version) have an export property?
2. What is a graceful / standard way of working around this while still allowing for require imports? I would settle for simple instructions for my users, but would prefer something I can do to better prepare for their use cases.

Not supporting require and providing only the es (.js) module files, I get this (the result of trying to require an ES module):

Error [ERR_REQUIRE_ESM]: require() of ES Module C:UsersjrungeDocumentsCODEpubsubdistslim.copper.js from C:UsersjrungeDocumentsCODEcopper_testsrcindex.js not supported.
Instead change the require of slim.copper.js in C:UsersjrungeDocumentsCODEcopper_testsrcindex.js to a dynamic import() which is available in all CommonJS modules.
    at Object.<anonymous> (C:UsersjrungeDocumentsCODEcopper_testsrcindex.js:3:16) {
  code: 'ERR_REQUIRE_ESM'
}