Exploring Redux Observable: An alternative to Redux Thunk and Saga

If you are working with Redux, you might have already heard of Redux Thunk and Saga, two popular middleware libraries for handling asynchronous actions. However, there is another library that is gaining popularity in the Redux community: Redux Observable. In this article, we will explore what Redux Observable is, how it works, and why it can be a good alternative to Redux Thunk and Saga.

What is Redux Observable?

Redux Observable is a middleware library for Redux that allows you to handle asynchronous actions using reactive programming concepts. It is based on the RxJS library, which is a powerful library for reactive programming in JavaScript.

With Redux Observable, you can create observables that emit actions, and then use operators to transform and combine these observables in various ways. This allows you to create complex asynchronous logic in a declarative and composable way.

How Redux Observable works

Let's take a look at a simple example of how Redux Observable works. Suppose you have a button in your UI that, when clicked, should fetch some data from an API and then dispatch an action with that data. Here's how you can handle this with Redux Observable:

import { ofType } from 'redux-observable';
import { ajax } from 'rxjs/ajax';
import { map, mergeMap } from 'rxjs/operators';

const FETCH_DATA = 'FETCH_DATA';
const FETCH_DATA_SUCCESS = 'FETCH_DATA_SUCCESS';

const fetchData = () => ({ type: FETCH_DATA });
const fetchDataSuccess = (data) => ({ type: FETCH_DATA_SUCCESS, payload: data });

const fetchDataEpic = (action$) => action$.pipe(
  ofType(FETCH_DATA),
  mergeMap(() => ajax.getJSON('https://example.com/data')),
  map((data) => fetchDataSuccess(data))
);

// Usage in a functional component:
// import { useDispatch } from 'react-redux';
// import { fetchData } from './actions';
// ...
// const dispatch = useDispatch();
// dispatch(fetchData());

export { fetchData, fetchDataEpic };

Let's break this down step by step:

1. First, we define two action types: FETCH_DATA and FETCH_DATA_SUCCESS.
2. We define two action creators: fetchData() and fetchDataSuccess(data). The fetchData() action creator returns an action with the type FETCH_DATA, while the fetchDataSuccess(data) action creator returns an action with the type FETCH_DATA_SUCCESS and a payload of data.
3. We define an epic called fetchDataEpic that takes an action$ stream as input and returns an output stream. The action$ stream represents a stream of actions dispatched to the Redux store.
4. We use the ofType operator from Redux Observable to filter out only the FETCH_DATA actions from the action$ stream.
5. We use the mergeMap operator from RxJS to map each FETCH_DATA action to an AJAX request that fetches some data from the API.
6. We use the map operator from RxJS to transform the response data into a FETCH_DATA_SUCCESS action.
7. Finally, we return the output stream from the fetchDataEpic function.

When the fetchData() action is dispatched, it is picked up by the fetchDataEpic epic. The epic then sends an AJAX request to the API to fetch some data, and then maps the response data to a FETCH_DATA_SUCCESS action, which is dispatched to the Redux store.

Why use Redux Observable?

So, why would you want to use Redux Observable instead of Redux Thunk or Saga? Here are a few reasons:

Declarative and Composable

One of the main advantages of Redux Observable is that it allows you to handle asynchronous logic in a declarative and composable way. By using observables and operators, you can easily define complex asynchronous workflows that are easy to reason about and modify.

Reactive Programming

Another advantage of Redux Observable is that it is based on reactive programming concepts, which can be a powerful way to handle asynchronous logic. Reactive programming allows you to think about asynchronous workflows as streams of events, and provides a wide range of operators for manipulating and transforming these streams.

Better Error Handling

Redux Observable also provides better error handling compared to Redux Thunk and Saga. When an error occurs in an epic, you can catch and handle it in a centralized way, which makes it easier to manage errors across your application.

Easy Testing

Because Redux Observable allows you to define asynchronous logic in a declarative way, it is also easier to test compared to Redux Thunk and Saga. You can use Jest or other testing frameworks to test your epics in isolation, without having to worry about complex control flow or side effects.

Conclusion

Redux Observable is a powerful middleware library for handling asynchronous actions in Redux. It provides a declarative and composable way to handle complex asynchronous logic, based on reactive programming concepts. While Redux Thunk and Saga are still popular choices for handling asynchronous actions in Redux, Redux Observable provides a compelling alternative that can simplify your code and make it easier to manage asynchronous workflows across your application.