simulateSlowAjax.js

const fetchContent = (url) => {
  const timeDelay$ = Rx.Observable.timer(1000);
  const request$ =  Rx.Observable.create(observer =>
    fetch(url, { mode: 'no-cors' })
      .then(json => {
        console.log('test')
         observer.onNext(json)
         observer.onCompleted()
      })
      .catch(e => observer.onError())
  )
  return timeDelay$.concat(request$);
}