Generator

function getIdInDb () {
  // Simulate async Db request
  setTimeout(function() {
    tmp.next(2); // I return 2 as a result for my Id
  }, 2000);
}

// Use the id returned by the yielded function
function getUserWithId (id) {
  console.log('Getting user with id:', id);
}

function *doSomethingInTheDb () {
  let id = yield getIdInDb();
  console.log('The id is:', id);
  getUserWithId(id);
}

// Stock the generator
var tmp = doSomethingInTheDb();

// Trigger the first yield
tmp.next();