How to resolve require vs. import in a Node.js script

Question

I'm doing a small Node.js script, where I wanted to use:

• https://github.com/heapwolf/prompt-sync
• https://github.com/sindresorhus/load-json-file

in the same file. But I'm struggling on how to import both libraries at the same time.

If my type package.json type is commonJs:

• I get SyntaxError: Cannot use import statement outside a module when trying to import import { loadJsonFile } from "load-json-file"
• I get Error [ERR_REQUIRE_ESM]: require() of ES Module D:\Dev\my-project\node_modules\load-json-file\index.js from D:\Dev\fsvl-date-check\index.js not supported. Instead change the require of D:\Dev\my-project\node_modules\load-json-file\index.js in D:\Dev\my-project\index.js to a dynamic import() which is available in all CommonJS modules. if I try to load with require("load-json-file")().

Now if I try to switch my package.json to module:

• I get SyntaxError: Named export 'prompt' not found. The requested module 'prompt-sync' is a CommonJS module, which may not support all module.exports as named exports. when I try to import like this: import { prompt } from "prompt-sync";.
• I get ReferenceError: require is not defined in ES module scope, you can use import instead if I try to import it like this: var prompt = require("prompt-sync")();

How can I use both those packages in the same project?

Answer 1

From within a ES module ("type": "module"):

You want to do import prompt from 'prompt-sync';. While you can fully import commonjs modules from ES modules, there are no named exports. So you can only import the default export. Either of these lines work and do the same:

import { default as prompt} from 'prompt-sync';
import prompt from 'prompt-sync';

This is because an commonjs module has only one export.

From within a commonjs module

To import a ES module you need to do dynamic import, as stated by the error message:

const loadJsonFileModule = await import('load-json-file');

import() return a Promise, resolving to a module. So you need to call it from within an async function, or use .then to resolve the promise.

Then loadJsonFileModule is a module, wrapping all the exports, not the default export. So you will need to do something like loadJsonFileModule.loadJsonFile(...).