.js

const { createFoo } = require('@foo-bar/core');

// option 1: have the factory/constructor take a 'blueprint' object 
const myFoo = createFoo({
  fooProp: 123,
  barProp: 'abc',
  fooFn() { 
    // ...
  },
  barFn() {
    // ...
  },
});

// option 2: create a blank Thing (or minimal options Thing) and then append to it
const myFoo = createFoo({ barProp: 'abc' });

myFoo.fooFn = function() {
  // ...
}

myFoo.barFn = function() {
  // ...
}