bs2.js

function BulkLoader(){
  this.users = [];
  this.companies = [];
  this.contacts = [];
};

BulkLoader.prototype.iterator = function * () {
  this.users = yield [{name: 'bob', email: 'bob@hotmail.com'}];
  this.contacts = yield [{name: 'brian', email: 'brian@hotmail.com'}];
  this.companies = yield [{name: 'company', email: 'company@hotmail.com'}];

  return this;
};

var iterator = new BulkLoader().iterator()

var users = iterator.next();
var contacts = iterator.next(users.value);
var companies = iterator.next(contacts.value);

var result = iterator.next(companies.value).value;

console.log(result.users);
console.log(result.contacts);
console.log(result.companies);