A library that ports Elm's effect system to Redux
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A port of Elm Architecture Cmd to Redux that allows you to express effects like HTTP requests by returning them from your reducers.

Looking for the v2 docs? Find them here.


Credit for the ideas and concepts that go into this library to Evan Czaplicki and all of the work he and others have put into Elm. Thanks also to Folktale.js for inspiration on the implementation and method naming on Tasks.


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.


Potential bugs, generally 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.


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