/esm-in-cjs-ts-demo

Demo of how to use ESM modules in CommonJS module with TypeScript

Primary LanguageTypeScript

Demo of how to use ESM modules in CommonJS module with TypeScript

Demonstrating how to use ESM-only packages node-fetch@3 and got@12 in a commonjs project. As well as using import from node:child_process.

For TS v5.0 see ts-50 branch

Running it

  1. git clone https://github.com/Maxim-Mazurok/esm-in-cjs-ts-demo && cd esm-in-cjs-ts-demo
  2. nvm i - make sure to use node/npm versions from "engines" section of the package.json
  3. npm ci - install deps
  4. npm start - compile and run
  5. Observe: 
    [Function: spawn]
Fetched with node-fetch:  <ref *1> Gunzip {...
Fetched with got:  {"login":"Maxim-Mazurok",...

Notes

  • Need "esModuleInterop": true to resolve Module '"node:http"' has no default export error and similar
  • Need "module": "Node16" or others to resolve Dynamic imports are only supported when the '--module' flag is set to 'es2020', 'es2022', 'esnext', 'commonjs', 'amd', 'system', 'umd', 'node16', or 'nodenext'.
  • Need "module": "Node16" to allow using import instead of require(), resolves Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension. error in import { spawn } from "child_process";
  • Need "moduleResolution": "Node16" to resolve Cannot find module 'node-fetch'. Did you mean to set the 'moduleResolution' option to 'nodenext', or to add aliases to the 'paths' option?
  • Don't really need to add "type": "commonjs" in package.json because module is assumed to be commonjs unless it has "type": "module" in package.json. tsconfig doesn't seem to affect that.
  • Need to use (async () => {...})() pattern to resolve 'await' expressions are only allowed at the top level of a file when that file is a module, but this file has no imports or exports. Consider adding an empty 'export {}' to make this file a module.
  • Need to use dynamic imports to resolve The current file is a CommonJS module whose imports will produce 'require' calls; however, the referenced file is an ECMAScript module and cannot be imported with 'require'. Consider writing a dynamic 'import("got")' call instead. To convert this file to an ECMAScript module, change its file extension to '.mts' or create a local package.json file with { "type": "module" }
  • Can't use "moduleResolution": "nodenext" with "module": "CommonJS", they need to match since TS 5.2, see https://devblogs.microsoft.com/typescript/announcing-typescript-5-2/#module-and-moduleresolution-must-match-under-recent-node-js-settings