Predictable state container for JavaScript apps
arpitpandey0209 and markerikson Add dev.to link as a learning resource (#3176)
[DEV Community](https://dev.to) Community is a burgeoning source of guidance and discussion on software topics, especially web dev. This will be a useful link to point to the official place to discuss Redux matters on the platform.

A few additional links pertaining to [dev.to](https://dev.to)

Traffic stats: https://www.similarweb.com/website/dev.to
Twitter: https://twitter.com/thepracticaldev
Redux tag (as included in PR): https://dev.to/t/redux

Some example Redux posts:
https://dev.to/oathkeeper/learning-redux-and-notes--43ae
https://dev.to/websavi/how-to-code-split-redux-store-to-further-improve-your-apps-performance-4gg9
https://dev.to/saigowthamr/build-your-own-redux-from-scratch-5a4d
https://dev.to/bnorbertjs/async-react-basics-with-redux-thunk--redux-saga-4af7

Happy coding ❤️
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README.md

Redux Logo

Redux is a predictable state container for JavaScript apps.
(Not to be confused with a WordPress framework – Redux Framework.)

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).

build status npm version npm downloads redux channel on discord Changelog #187

Learn Redux

We have a variety of resources available to help you learn Redux, no matter what your background or learning style is.

Just the Basics

If you're brand new to Redux and want to understand the basic concepts, see:

Intermediate Concepts

Once you've picked up the basics of working with actions, reducers, and the store, you may have questions about topics like working with asynchronous logic and AJAX requests, connecting a UI framework like React to your Redux store, and setting up an application to use Redux:

Real-World Usage

Going from a TodoMVC app to a real production application can be a big jump, but we've got plenty of resources to help:

Finally, Mark Erikson is teaching a series of Redux workshops through Workshop.me. Check the workshop schedule for upcoming dates and locations.

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!

Before Proceeding Further

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

Yes, these guidelines are subjective and vague, but this is for good reason. The point at which you should integrate Redux into your application is different for every user and different for every application.

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

Developer Experience

Dan Abramov (author of Redux) wrote Redux while working on his React Europe talk called “Hot Reloading with Time Travel”. His goal was to create a state management library with a minimal API but completely predictable behavior. Redux makes it possible to implement logging, hot reloading, time travel, universal apps, record and replay, without any buy-in from the developer.

Influences

Redux evolves the ideas of Flux, but avoids its complexity by taking cues from Elm.
Even if you haven't used Flux or Elm, Redux only takes a few minutes to get started with.

Installation

To install the stable version:

npm install --save redux

This assumes you are using npm as your package manager.

If you're not, you can access these files on unpkg, download them, or point your package manager to them.

Most commonly, people consume Redux as a collection of CommonJS modules. These modules are what you get when you import redux in a Webpack, Browserify, or a Node environment. If you like to live on the edge and use Rollup, we support that as well.

If you don't use a module bundler, it's also fine. The redux npm package includes precompiled production and development UMD builds in the dist folder. They can be used directly without a bundler and are thus compatible with many popular JavaScript module loaders and environments. For example, you can drop a UMD build as a <script> tag on the page, or tell Bower to install it. The UMD builds make Redux available as a window.Redux global variable.

The Redux source code is written in ES2015 but we precompile both CommonJS and UMD builds to ES5 so they work in any modern browser. You don't need to use Babel or a module bundler to get started with Redux.

Complementary Packages

Most likely, you'll also need the React bindings and the developer tools.

npm install --save react-redux
npm install --save-dev redux-devtools

Note that unlike Redux itself, many packages in the Redux ecosystem don't provide UMD builds, so we recommend using CommonJS module bundlers like Webpack and Browserify for the most comfortable development experience.

The Gist

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.

If you're coming from Flux, there is a single important difference you need to understand. Redux doesn't have a Dispatcher or support many stores. Instead, there is just a single store with a single root reducing function. As your app grows, instead of adding stores, 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 from Its Authors

Redux Video Tutorials by Dan Abramov

Getting Started with Redux

Getting Started with Redux is a video course consisting of 30 videos narrated by Dan Abramov, author of Redux. It is designed to complement the “Basics” part of the docs while bringing additional insights about immutability, testing, Redux best practices, and using Redux with React. This course is free and will always be.

“Great course on egghead.io by @dan_abramov - instead of just showing you how to use #redux, it also shows how and why redux was built!”
Sandrino Di Mattia

“Plowing through @dan_abramov 'Getting Started with Redux' - its amazing how much simpler concepts get with video.”
Chris Dhanaraj

“This video series on Redux by @dan_abramov on @eggheadio is spectacular!”
Eddie Zaneski

“Come for the name hype. Stay for the rock solid fundamentals. (Thanks, and great job @dan_abramov and @eggheadio!)”
Dan

“This series of videos on Redux by @dan_abramov is repeatedly blowing my mind - gunna do some serious refactoring”
Laurence Roberts

So, what are you waiting for?

Watch the free "Getting Started with Redux" video series

Note: If you enjoyed Dan's course, consider supporting Egghead by buying a subscription. Subscribers have access to the source code of every example in my videos and tons of advanced lessons on other topics, including JavaScript in depth, React, Angular, and more. Many Egghead instructors are also open source library authors, so buying a subscription is a nice way to thank them for the work that they've done.

Building React Applications with Idiomatic Redux

The Building React Applications with Idiomatic Redux course is a second free video series by Dan Abramov. It picks up where the first series left off, and covers practical production ready techniques for building your React and Redux applications: advanced state management, middleware, React Router integration, and other common problems you are likely to encounter while building applications for your clients and customers. As with the first series, this course will always be free.

Watch the free "Idiomatic Redux" video series

Practical Redux course

Practical Redux is a paid interactive course by Redux co-maintainer Mark Erikson. The course is designed to show how to apply the basic concepts of Redux to building something larger than a TodoMVC application. It includes real-world topics like:

  • Adding Redux to a new Create-React-App project and configuring Hot Module Replacement for faster development
  • Controling your UI behavior with Redux
  • Using the Redux-ORM library to manage relational data in your Redux store
  • Building a master/detail view to display and edit data
  • Writing custom advanced Redux reducer logic to solve specific problems
  • Optimizing performance of Redux-connected form inputs

And much more!

The course is based on Mark's original free "Practical Redux" blog tutorial series, but with updated and improved content.

Redux Fundamentals Workshop

Redux co-maintainer Mark Erikson has put together a Redux Fundamentals workshop, and slides are available here. They cover:

  • The history and purpose of Redux
  • Reducers, actions, and working with a Redux store
  • Using Redux with React
  • Using and writing Redux middleware
  • Working with AJAX calls and other side effects
  • Unit testing Redux apps
  • Real-world Redux app structure and development

Documentation

For PDF, ePub, and MOBI exports for offline reading, and instructions on how to create them, please see: paulkogel/redux-offline-docs.

For Offline docs, please see: devdocs

Examples

Almost all examples have a corresponding CodeSandbox sandbox. This is an interactive version of the code that you can play with online.

If you're new to the NPM ecosystem and have troubles getting a project up and running, or aren't sure where to paste the gist above, check out simplest-redux-example that uses Redux together with React and Browserify.

Testimonials

“Love what you're doing with Redux”
Jing Chen, creator of Flux

“I asked for comments on Redux in FB's internal JS discussion group, and it was universally praised. Really awesome work.”
Bill Fisher, author of Flux documentation

“It's cool that you are inventing a better Flux by not doing Flux at all.”
André Staltz, creator of Cycle

Thanks

Special thanks to Jamie Paton for handing over the redux NPM package name.

Logo

You can find the official logo on GitHub.

Change Log

This project adheres to Semantic Versioning.
Every release, along with the migration instructions, is documented on the GitHub Releases page.

Patrons

The work on Redux was funded by the community.
Meet some of the outstanding companies that made it possible:

See the full list of Redux patrons, as well as the always-growing list of people and companies that use Redux.

License

MIT