A simple way to create objects usable to extends other objects or classes.

extensible.js

function extensible(object) {
  // usable to extend a class
  function descriptors() {}
  // get rid of name, length, and the rest
  Reflect.ownKeys(descriptors).forEach(function (k) {
    delete descriptors[k];
  });
  // clean up the constructor too
  descriptors.prototype = {};
  // per each property in object
  Reflect.ownKeys(object).forEach(function (k) {
    // grab the descriptor
    var d = Object.getOwnPropertyDescriptor(object, k);
    // if it's a Proxy trap, ignore it
    if (!d) return;
    // make it non enumerable, no matter what
    d.enumerable = false;
    // define it as prototype property
    Object.defineProperty(descriptors.prototype, k, d);
    // define it also as descriptor
    Object.defineProperty(descriptors, k, {
      enumerable: true,
      value: d
    });
  });
  // the exensible object is here
  return descriptors;
}


// example
const greeter = extensible({
  greetings() {
    console.log('Hello world from ' + this.name);
  }
});

// usable to extend a class
class Greeter extends greeter {
  constructor(name) {
    super();
    this.name = name;
  }
}

const
  gClass = new Greeter('class'),
  // usable to enrich a created object
  gObject = Object.create({name: 'object'}, greeter)
;

gClass.greetings();
gObject.greetings();