redux-observable-api-hoc.js

import { combineEpics } from 'redux-observable';

/*
 * Let's assume each configuration has the following:
 * {
 *   type: String|Array<String>,
 *   url: String,
 *   method: String,
 *   body: String|Function<Action, String|Object>,
 *   process: Function<ActionObservable, ActionObservable>,
 *   latest: Boolean // true for switchMap
 * }
 */

function createApiEpic(configurations) {
  var epics = configurations.map(config => {
    const actionTypes = Array.isArray(config.type) ? config.type : [config.type];
    
    const requestProcessor = action => {
      /* Here you create your ajax observable and do proper handling of request/response */
    };
    
    return action$ => {
      let stream$ = action$.ofType(actionTypes);
      stream$ = config.latest ? stream$.mergeMap(requestProcessor) : stream$.switchMap(requestProcessor);
      return typeof config.process === 'function' ? config.process(stream$) : stream$;
    }
  });
  
  return combineEpics(epics);
}

const ajaxApiEpic = createApiEpic([
  {
    type: 'SAVE_MY_DATA',
    url: `/api/mydata/${myId}`,
    method: 'PATCH',
    latest: true,
    body: action => action.data,
    process: actions$ => actions$.debounceTime(400).retry(2)
  }
]);


// Then when configuring the middleware

const rootEpic = combineEpics(
  ajaxApiEpic,
  // ... your other epics
);

const middleware = createEpicMiddleware(rootEpic);