Getting Started with Redux

Redux is a predictable state container for JavaScript apps.

It helps you write applications that behave consistently, run in different environments (client, server, and native), and are easy to test. On top of that, it provides a great developer experience, such as live code editing combined with a time traveling debugger.

You can use Redux together with React, or with any other view library. It is tiny (2kB, including dependencies), but has a large ecosystem of addons available.

Installation

Redux Toolkit

Redux Toolkit is our official recommended approach for writing Redux logic. It wraps around the Redux core, and contains packages and functions that we think are essential for building a Redux app. Redux Toolkit builds in our suggested best practices, simplifies most Redux tasks, prevents common mistakes, and makes it easier to write Redux applications.

RTK includes utilities that help simplify many common use cases, including store setup, creating reducers and writing immutable update logic, and even creating entire "slices" of state at once.

Whether you're a brand new Redux user setting up your first project, or an experienced user who wants to simplify an existing application, Redux Toolkit can help you make your Redux code better.

Redux Toolkit is available as a package on NPM for use with a module bundler or in a Node application:

# NPM

npm install @reduxjs/toolkit

# Yarn

yarn add @reduxjs/toolkit

Create a React Redux App

The recommended way to start new apps with React and Redux is by using the official Redux+JS template for Create React App, which takes advantage of Redux Toolkit and React Redux's integration with React components.

npx create-react-app my-app --template redux

Redux Core

The Redux core library is available as a package on NPM for use with a module bundler or in a Node application:

# NPM

npm install redux

# Yarn

yarn add redux

It is also available as a precompiled UMD package that defines a window.Redux global variable. The UMD package can be used as a <script> tag directly.

For more details, see the Installation page.

Basic Example

The whole state of your app is stored in an object tree inside a single store. The only way to change the state tree is to emit an action, an object describing what happened. To specify how the actions transform the state tree, you write pure reducers.

That's it!

import { createStore } from 'redux'

/**

* This is a reducer, a pure function with (state, action) => state signature.

* It describes how an action transforms the state into the next state.

*

* The shape of the state is up to you: it can be a primitive, an array, an object,

* or even an Immutable.js data structure. The only important part is that you should

* not mutate the state object, but return a new object if the state changes.

*

* In this example, we use a `switch` statement and strings, but you can use a helper that

* follows a different convention (such as function maps) if it makes sense for your

* project.

*/

function counter(state = 0, action) {

switch (action.type) {

case 'INCREMENT':

return state + 1

case 'DECREMENT':

return state - 1

default:

return state

}

}

// Create a Redux store holding the state of your app.

// Its API is { subscribe, dispatch, getState }.

let store = createStore(counter)

// You can use subscribe() to update the UI in response to state changes.

// Normally you'd use a view binding library (e.g. React Redux) rather than subscribe() directly.

// However it can also be handy to persist the current state in the localStorage.

store.subscribe(() => console.log(store.getState()))

// The only way to mutate the internal state is to dispatch an action.

// The actions can be serialized, logged or stored and later replayed.

store.dispatch({ type: 'INCREMENT' })

// 1

store.dispatch({ type: 'INCREMENT' })

// 2

store.dispatch({ type: 'DECREMENT' })

// 1

Instead of mutating the state directly, you specify the mutations you want to happen with plain objects called actions. Then you write a special function called a reducer to decide how every action transforms the entire application's state.

In a typical Redux app, there is just a single store with a single root reducing function. As your app grows, you split the root reducer into smaller reducers independently operating on the different parts of the state tree. This is exactly like how there is just one root component in a React app, but it is composed out of many small components.

This architecture might seem like an overkill for a counter app, but the beauty of this pattern is how well it scales to large and complex apps. It also enables very powerful developer tools, because it is possible to trace every mutation to the action that caused it. You can record user sessions and reproduce them just by replaying every action.

Learn Redux

We have a variety of resources available to help you learn Redux.

Redux Essentials Tutorial

The Redux Essentials tutorial is a "top-down" tutorial that teaches how to use Redux the right way, using our latest recommended APIs and best practices. We recommend starting there.

Additional Tutorials

• The Redux docs Basic tutorial and Advanced tutorial are a "bottom-up" tutorial that teaches how Redux works, starting from first principles.
• The Redux repository contains several example projects demonstrating various aspects of how to use Redux. Almost all examples have a corresponding CodeSandbox sandbox. This is an interactive version of the code that you can play with online. See the complete list of examples in the Examples page.
• Redux creator Dan Abramov's free "Getting Started with Redux" video series and Building React Applications with Idiomatic Redux video courses on Egghead.io
• Redux maintainer Mark Erikson's "Redux Fundamentals" conference talk and "Redux Fundamentals" workshop slides
• Dave Ceddia's post A Complete React Redux Tutorial for Beginners

Other Resources

• The Redux FAQ answers many common questions about how to use Redux, and the "Recipes" docs section has information on handling derived data, testing, structuring reducer logic, and reducing boilerplate.
• Redux maintainer Mark Erikson's "Practical Redux" tutorial series demonstrates real-world intermediate and advanced techniques for working with React and Redux (also available as an interactive course on Educative.io).
• The React/Redux links list has categorized articles on working with reducers and selectors, managing side effects, Redux architecture and best practices, and more.
• Our community has created thousands of Redux-related libraries, addons, and tools. The "Ecosystem" docs page lists our recommendations, and there's a complete listing available in the Redux addons catalog.

Help and Discussion

The #redux channel of the Reactiflux Discord community is our official resource for all questions related to learning and using Redux. Reactiflux is a great place to hang out, ask questions, and learn - come join us!

You can also ask questions on Stack Overflow using the #redux tag.

If you have a bug report or need to leave other feedback, please file an issue on the Github repo

Should You Use Redux?

Redux is a valuable tool for organizing your state, but you should also consider whether it's appropriate for your situation. Don't use Redux just because someone said you should - take some time to understand the potential benefits and tradeoffs of using it.

Here are some suggestions on when it makes sense to use Redux:

• You have reasonable amounts of data changing over time
• You need a single source of truth for your state
• You find that keeping all your state in a top-level component is no longer sufficient

For more thoughts on how Redux is meant to be used, see:

• Redux FAQ: When should I use Redux?

• You Might Not Need Redux

• The Tao of Redux, Part 1 - Implementation and Intent

• The Tao of Redux, Part 2 - Practice and Philosophy

• Redux FAQ