RxJS Playground

A blank canvas to play / experiment with RxJS: https://github.com/Reactive-Extensions/RxJS

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/4.0.7/rx.all.js"></script>

JavaScript

function getKeyFromEvent(ev) {return ev.key}
function isKeyPressedIsO(ev) {return getKeyFromEvent(ev) === 'o'}

const KEY = 'key';
const TIMER = 'timer';
const COMBO = 'combo';
const SIMPLE_KEY = 'whatever';
const timeSpanInMs = 1000;
const keyup$ = Rx.Observable.fromEvent(document, 'keyup')
  .map(ev => ({event: KEY, data: getKeyFromEvent(ev)}));
const keyupTimer$ = keyup$.flatMapLatest(eventStruct => 
  Rx.Observable.of(eventStruct)
//    .tap(console.warn.bind(console, 'timer event'))
    .delay(timeSpanInMs)
    .map(() => ({event : TIMER, data: null}))
    );

Rx.Observable.merge(keyup$, keyupTimer$)
//  .tap(console.warn.bind(console))
  .scan((acc, eventStruct) => {
    if (acc.control === SIMPLE_KEY) {
      if (eventStruct.event === KEY) {
        if (eventStruct.data === `o`) {
          return {control: COMBO, keyOrKeys : []}
        }
        else {
          return {control: SIMPLE_KEY, keyOrKeys : eventStruct.data}
        }
      }
      else {
      // TIMER event
        return {control: SIMPLE_KEY, keyOrKeys : null}
      }
    }
    else {
      // we only have two states, so it is COMBO state here
      if (eventStruct.event === KEY) {
        return {control: COMBO, keyOrKeys : acc.keyOrKeys.concat([eventStruct.data])}
      }
      else {
        // this is a TIMER event, we only have two events
        return {control: SIMPLE_KEY, keyOrKeys : acc.keyOrKeys}
      }
    }
  }, {control: SIMPLE_KEY, keyOrKeys : null})
//  .tap(console.warn.bind(console))
  .filter(state => state.keyOrKeys) // TIMER event in SIMPLE_KEY state
  .map (({control, keyOrKeys}) => {
  // Here you associate your action
  // if keyOrKeys is an array, then you have a combo
  // else you have a single key
  console.log('key(s) pressed', keyOrKeys)
  return keyOrKeys
})
  .subscribe (console.log.bind(console))