A library that ports Elm's effect system to Redux
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A port of the Elm Architecture to Redux that allows you to sequence your effects naturally and purely by returning them from your reducers.

Isn't it incorrect to cause side-effects in a reducer?

Yes! Absolutely.

Doesn't redux-loop put side-effects in the reducer?

It doesn't. The values returned from the reducer when scheduling an effect with redux-loop only describe the effect. Calling the reducer will not cause the effect to run. The value returned by the reducer is just an object that the store knows how to interpret when it is enhanced by redux-loop. You can safely call a reducer in your tests without worrying about waiting for effects to finish and what they will do to your environment.

What are the environment requirements for redux-loop?

redux-loop requires polyfills for ES6 Promise and Symbol to be included if the browsers you target don't natively support them.

Why use this?

Having used and followed the progression of Redux and the Elm Architecture, and after trying other effect patterns for Redux, we came to the following conclusion:

Synchronous state transitions caused by returning a new state from the reducer in response to an action are just one of all possible effects an action can have on application state.

Many other methods for handling effects in Redux, especially those implemented with action-creators, incorrectly teach the user that asynchronous effects are fundamentally different from synchronous state transitions. This separation encourages divergent and increasingly specific means of processing particular types effects. Instead, we should focus on making our reducers powerful enough to handle asynchronous effects as well as synchronous state transitions. With redux-loop, the reducer doesn't just decide what happens now due to a particular action, it decides what happens next. All of the behavior of your application can be traced through one place, and that behavior can be easily broken apart and composed back together. This is one of the most powerful features of the Elm architecture, and with redux-loop it is a feature of Redux as well.


npm install --save redux-loop


Potential bugs, general discussion, and proposals or RFCs should be submitted as issues to this repo, we'll do our best to address them quickly. We use this library as well and want it to be the best it can! For questions about using the library, submit questions on StackOverflow with the redux-loop tag.

Slack channel

Come join our slack channel.

Don't see a feature you want?

If you're interested in adding something to redux-loop but don't want to wait for us to incorporate the idea you can follow these steps to get your own installable version of redux-loop with your feature included:

  1. Fork the main repo here
  2. Add your feature or change
  3. Change the package "name" in package.json to be "@<your-npm-username>/redux-loop
  4. Commit to master and npm publish
  5. npm install @<your-npm-username>/redux-loop

We are always interested in new ideas, but sometimes we get a little busy and fall behind on responding and reviewing PRs. Hopefully this process will allow you to continue making progress on your projects and also provide us with more context if and when you do decide to make a PR for your new feature or change. The best way to verify new features for a library is to use them in real-world scenarios!


Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms. Multiple language translations are available at contributor-covenant.org