How to handle (asynchronous) side effects in Redux?

In Redux, the concept of handling side effects is typically accomplished through middleware. The most common tools for handling asynchronous side effects in Redux are:

1. Redux Thunk: This is the most popular middleware for Redux. Redux Thunk supports asynchronous actions (i.e., functions that return functions) and gives you direct access to the dispatch method.

1. Redux Saga: It uses generators to make asynchronous code look like synchronous code and offer more control over the flow. In addition to handling side effects, you can also pause and cancel asynchronous actions.

1. Redux Observable (RxJS): Like Redux Saga, this uses Observables to handle asynchronous actions.

Steps to handle asynchronous side effects using Redux Thunk:

a. First, you need to apply Redux Thunk middleware.

b. Then, instead of returning action objects from your action creators, you may return a function that controls the dispatching. That way, you even dispatch multiple times from within your function!

```
function myAsyncAction() { return dispatch => { dispatch({type: ‘START_ASYNC’});

someAsyncFunction().then( result => dispatch({type: ‘ASYNC_SUCCESS’, payload: result}), error => dispatch({type: ‘ASYNC_FAILURE’, error: error}) ); }; } ``` In this example, you start by dispatching a synchronous action to notify Redux that you have started a collection of asynchronous tasks. Then, when your async function (a promise, a timeout, etc.) resolves, you dispatch a success action with the result. If it fails, you dispatch an error action with the error.

Remember that it’s important to handle errors and edge cases in your UI and state, not just in your async code. This is because if you don’t handle the error in your async code, the error will propagate to your reducer and the state may become inconsistent.

These libraries are not part of Redux itself, but they define a pattern of handling side effects and they are wildly used in the Redux community.