const cities = [

  'London',

  'Madrid',

  'Brussels',

  'Praha',

  'Berlin',

  'Marseille',

  'Bukarest'

]

​

const subject = new Rx.Subject()

const onChange = e => subject.onNext(e.target.value)

​

const citiesStream = Rx.Observable.combineLatest(

  Rx.Observable.return(cities),

  subject.debounce(1500).startWith(''),

  (cities, i) => cities.filter(city => city.match(new RegExp(i, 'i')))

)

.do(console.log)

​

const Cities = React.createClass({

  render: function() {

    return (

      <div>

        <input type="text" onChange={onChange} />

        <ul>

        {this.props.cities.map(city =>

           <li key={city}>{city}</li>)}

        </ul>

      </div>

    )

  }

})

​

citiesStream.subscribe(cities => 

  ReactDOM.render(

    <Cities cities={cities} />,

    document.querySelector('#app')

  )

)

​