const showTyping = () =>

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

​

const showIdle = () =>

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

​

​

// user typing events are mapped to 1

const input$ = Rx.Observable

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

​

// user stopped typing

const stoppedTypingAfter1s$ = input$

  .switchMapTo(Rx.Observable.timer(1000));

​

// we merge the streams together

const state$ = Rx.Observable.merge(

    input$.mapTo(1),

    stoppedTypingAfter1s$.mapTo(0)

)

  .startWith(0)

  .do(val => val === 0 ? showIdle() : showTyping())

  .subscribe(console.log);