redux-observable-type-and-observable.js

import 'rxjs';
import { combineEpics } from 'redux-observable';

// Use RxJS ajax
const fetchEpic = (action$) =>
  action$.ofType('FETCH_REQUESTED')
    .mergeMap(action => Observable.ajax.get(action.payload.url))
    .map(data => ({ type: 'FETCH_SUCCEEDED', data }))
    .catch(error => Observable.of({ type: 'FETCH_FAILED', error }));

// Or simply use fetch
// const fetchEpic = (action$) =>
//   action$.ofType('FETCH_REQUESTED')
//     .mergeMap(fetch(action.payload.url).then(response => response.json()));
//     .map(data => { type: 'FETCH_SUCCEEDED', data })
//     .catch(error => Observable.of({ type: 'FETCH_FAILED', error }));

+export default combineEpics(
+  fetchEpic,
+);