React Answers

Why do we need middleware for async flow in Redux?

Spread the love

Middleware is crucial for handling asynchronous flow in Redux because Redux itself doesn’t have built-in support for handling asynchronous actions. Redux was designed to manage state and state transitions synchronously, meaning that by default, it doesn’t support handling asynchronous operations like fetching data from a server or interacting with a database.

Here’s why middleware is needed for asynchronous flow in Redux:

Pure Functions

Redux reducers must be pure functions, meaning they should not have side effects and should return the same output for the same input every time they are called. Asynchronous operations like API calls involve side effects and cannot be handled directly inside reducers.

Synchronous Nature

Redux’s built-in dispatch function is synchronous. It immediately triggers the reducer with an action object, which then updates the state. Asynchronous operations cannot be performed synchronously because they take time to complete, and the action dispatch needs to wait for them to finish before updating the state.


Middleware in Redux provides a way to intercept and modify actions that are dispatched to the store before they reach the reducer. This interception capability allows middleware to handle asynchronous actions by delaying the dispatch of actions or dispatching multiple actions based on the result of the asynchronous operation.

Thunks, Sagas, or Epics

Middleware libraries like Redux Thunk, Redux Saga, and Redux Observable provide mechanisms for handling asynchronous flow in Redux. They extend Redux’s capabilities by allowing you to dispatch functions (thunks), use generator functions (sagas), or work with observables (epics) to handle asynchronous operations and dispatch additional actions based on the results.

Separation of Concerns

By using middleware for asynchronous flow, you keep your action creators and reducers focused on managing state transitions, while the middleware handles asynchronous logic separately. This separation of concerns improves code organization and maintainability.

In summary, middleware is necessary for handling asynchronous flow in Redux because it allows Redux to remain synchronous while providing a mechanism to handle asynchronous operations separately and efficiently.

By John Au-Yeung

Web developer specializing in React, Vue, and front end development.

Leave a Reply

Your email address will not be published. Required fields are marked *