CJS to ESM

cjs.js

const something = require('something');
const { somethingElse } = require('something-else');

const { exports } = module;

exports.somethingElse = somethingElse;

module.exports = something;
Object.assign(module.exports, exports);

esm.js

// Replaced by transform
import something from 'something';
import { somethingElse } from 'something-else';

// Added by trasnform
let module = {
  exports: {}
};

const { exports } = module;

exports.somethingElse = somethingElse;

module.exports = something;
Object.assign(module.exports, exports);

// Added by transform
export default module.exports;

Dynamic require source value will be a separate issue to address, as it will involve using dynamic import.

Something like require('pat' + 'h') could get reduced down to require('path'), but const h = () => { return h; }(); require('pat' + h); won't be possible to flatten. We can rewrite it with something like:

const h = () => { return 'h'; }(); import('pat' + h);