require() not working in module type nodejs script

Question

In my package.json file I've specified that my nodejs app is of type module, because if I do not do that, it seems that I can not use import statements. This is how it looks like now:

{
  "name": "...",
  "version": "1.0.0",
  "description": "....",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "...."
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "lodash": "^4.17.15"
  },
  "type": "module"
}

But if I add the "type": "module" to my package.json file, I can't use require statements anymore, because I get a ReferenceError: require is not defined error.

If I remove the "type": "module" line from package.json, and rewrite all of my imports to requires, everything works without an error.

I can't seem to find any indication, that import and require can not be mixed or used together in the same script, am I missing something here, or I am having some other bug? How could I resolve to use these two kind of statements in the same script?

Why I would need this, is because I want to require some config files based on dynamic paths, and only if the files exists, which I think I can not do with import.

DISCLAIMER: I am rather new to nodejs server side programming, so it is possible that I am approaching this situation very wrongly, if that's the case, please advice me something, based on the Why I've mentioned above.

NOTE: I am running this node script from the server terminal, and not from the browser.

Answer 1

But if I add the "type": "module" to my package.json file, I can't use require statements anymore, because I get a ReferenceError: require is not defined error.

Right. It's either/or. Either you use ESM (JavaScript modules, type = "module") or you use CJS (CommonJS-like Node.js native modules, require).

But, if you're using type="module":

1. You can still use CJS modules, you just import them via import instead of require (or via import() [dynamic import] if necessary). See details here and here.

2. You can use createRequire to effectively get a require function you can use in your ESM module, which brings us to...

Why I would need this, is because I want to require some config files based on dynamic paths, and only if the files exists, which I think I can not do with import.

That's right. You have to use createRequire for that instead (or readFile and JSON.parse), more here.

createRequire version:

import { createRequire } from "module";
const require = createRequire(import.meta.url);
const yourData = require("./your.json");