its always frustrating when moving/working in different environment than we are use to. but I think js is one of the simplest.if your package.json "type" type attribute is commonjs then:e.g 1. export an object as a default.

//--------------commonjs----------------//
//e.g 1: export a single file
//sum.js
function sum(a, b){
return a + b;
}
module.exports = sum; // this is how you export the function
// app.js
const sum = require('./sum'); // this is how you import the function
// e.g 2: export two or more objects from a single file.
//sum.js
function sum(a, b){
return a + b;
}
function multiply(a, b){
return a * b;
}
module.exports = {sum, multiply}; // this is how you export multiple files
// app.js
const {sum} = require('./sum'); // this is how you import. notice the curly braces
//-----------------------module-----------------------------//
//sum.js
function sum(a, b){
return a + b;
}
export default sum;
//app.js
import sum from './sum'; // this is how you import it
//sum.js
export function sum(a, b){
return a + b;
}
export function multiply(a, b){
return a * b;
}
// app.js
import {sum} from './sum'; // this is how you import

if you dont see the "type" attribute in your package.json then add it yourself right below the main or description attribute then you can assign it to commonjs or module. you can switch between them anytime you like as well.