redux-effects-example.js

import Observable from 'rxjs/observable';

// Action creator function
function fetchArticles(params) {
 return { type: FETCH_ARTICLES, params };
}

// Epic
const fetchArticlesEpic = action$ => {
  return action$
    .ofType(FETCH_ARTICLES)
    .switchMap(action => {
      return Observable.concat(
        Observable.of({ type: FETCH_ARTICLES_START }),  
        Observable.fromPromise(
          ArticlesService.getArticles(action.params)
            .then(
              user => ({ type: FETCH_ARTICLES_SUCCESS, user }),
              error => ({ type: FETCH_ARTICLES_FAILURE, error })
            )
        )
      );
    });
}

// Configuration
const epicMiddleware = createEpicMiddleware(fetchArticlesEpic);
const store = createStore(
  reducer,
  applyMiddleware(epicMiddleware)
);

// Actual usage
dispatch(fetchArticles(params));