delegatePrototype.js

const fooProto = {
  data: {
    descriptor: 'bar'
  },
  printDescriptor: () => console.log(this.data.descriptor),
};

const foo1 = Object.create(fooProto);
const foo2 = Object.create(fooProto);

foo1.data = {descriptor: 'baz'};
foo2.printDescriptor();