event.js

// Minimal events

// type Listener := (value: Value) => void
// type Cancel := () => void
// type Event := (listener: Listener) => Cancel

// someEvent := Event<T>
function someEvent(listener) {
  // notify listener when an event has occured
  // want to signal completion? Invoke listener(Event.Completed)
  // want to signal rejection? Invoke listener(new Error(reason))

  return function cancel() {
    // remove listener from notification list.
  }
}