Seeking NodeJS + TypeScript Demo Project with CJS and ESM Exports

[UrielCh]

Hi,

Does anyone have a demo NodeJS + TypeScript project that serves as a best practice example for exporting with both CJS and ESM formats?

I've been unable to find a clear way to build a project that supports both pure CJS and pure ESM exports.

I believe there should be three types of project templates:

• CJS masquerading as ESM
• ESM masquerading as CJS
• Both pure ESM and pure CJS

Is it possible for a clean project to maintain a single set of typings? It seems like ESM and CJS might each require their own set of typings.

Thank you!

[andrewbranch]

ESM and CJS do necessarily require their own set of typings. I suggest looking at https://github.com/isaacs/tshy as a tool to generate both formats. However, I also suggest considering shipping ESM only as a best practice.

[atomicpages]

What @andrewbranch said. There's also https://tsup.egoist.dev/ for bundling ESM and CJS formats. You can do this pretty easily with their config:

import { defineConfig } from "tsup";

export default defineConfig({
  entry: ["src/index.ts"],
  splitting: false,
  format: ["esm", "cjs"],
  sourcemap: true,
  clean: true,
  dts: true,
});

If you don't want yet another tool then use this as a guide:

	File Ext	Package Type
CJS	.js, .d.ts	CommonJS
ESM	.mjs, .d.mts	CommonJS
CJS	.js, .d.ts	module
ESM	.cjs, .d.cts	module