console.clear();

​

/*** Render Functions ***/

​

const showTyping = () =>

  $('.typing').text('User is typing...');

​

const showIdle = () =>

  $('.typing').text('');

​

const updateTimer = ms =>

  $('.timer').text(ms / 1000);

​

/*** Program Logic ***/

​

const typing$ = Rx.Observable

  .fromEvent($('#input'), 'input')

  .switchMapTo(Rx.Observable

               .never()

               .startWith('TYPING')

               .merge(Rx.Observable.timer(1000).mapTo('IDLE')))

  .do(e => e === 'TYPING' ? showTyping() : showIdle());

​

const isTyping$ = typing$

  .distinctUntilChanged()

  .map(e => e === "TYPING")

  .publishReplay(1)

  .refCount();

​

const timer$ = isTyping$

  .switchMap(isTyping => isTyping ? Rx.Observable.interval(100) : Rx.Observable.never())

  .scan(totalMs => (totalMs + 100), 0)

  .subscribe(updateTimer);