Convert thunk to observable

thunkToObservable.js

function thunkToObservable(thunk) {
  return (getState, ...args) => {
    return new Observable(observer => {
      const dispatchProxy = new Subject();
      const dispatch = action => dispatchProxy.next(action);
      thunk(...args)(dispatch, getState);
      return dispatchProxy.subscribe(observer);
    });
  };
}