redux

What is 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. Redux provides a single source of truth for your application's state, making state mutations predictable through a strict unidirectional data flow.

What are redux's main functionalities?

State Management

Redux provides a store that holds the state tree of your application. You can dispatch actions to change the state, and subscribe to updates.

const { createStore } = require('redux');

function counter(state = 0, action) {
  switch (action.type) {
    case 'INCREMENT':
      return state + 1;
    case 'DECREMENT':
      return state - 1;
    default:
      return state;
  }
}

let store = createStore(counter);

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

store.dispatch({ type: 'INCREMENT' });
// The current state is 1
store.dispatch({ type: 'INCREMENT' });
// The current state is 2
store.dispatch({ type: 'DECREMENT' });
// The current state is 1

Actions

Actions are payloads of information that send data from your application to your store. They are the only source of information for the store.

function addTodo(text) {
  return {
    type: 'ADD_TODO',
    text
  };
}

store.dispatch(addTodo('Learn Redux'));

Reducers

Reducers specify how the application's state changes in response to actions sent to the store. Remember that actions only describe what happened, but don't describe how the application's state changes.

function todos(state = [], action) {
  switch (action.type) {
    case 'ADD_TODO':
      return state.concat([action.text]);
    default:
      return state;
  }
}

Middleware

Middleware extends Redux with custom functionality. It lets you wrap the store's dispatch method for fun and profit. A very common use is for dealing with asynchronous actions.

const { applyMiddleware, createStore } = require('redux');
const createLogger = require('redux-logger');

const logger = createLogger();
const store = createStore(
  reducer,
  applyMiddleware(logger)
);

Other packages similar to redux

mobx

MobX is a battle-tested library that makes state management simple and scalable by transparently applying functional reactive programming (TFRP). Unlike Redux, which uses a single store and requires you to dispatch actions to change your state, MobX allows you to create multiple stores and uses observables to automatically track changes in state through actions.

vuex

Vuex is a state management pattern + library for Vue.js applications. It serves as a centralized store for all the components in an application, with rules ensuring that the state can only be mutated in a predictable fashion. It is very similar to Redux but is tailored specifically for the Vue.js framework.

flux

Flux is the application architecture that Facebook uses for building client-side web applications. It complements React's composable view components by utilizing a unidirectional data flow. It's more of a pattern rather than a formal framework, and you can start using Flux immediately without a lot of new code. Redux was actually inspired by Flux and can be considered its evolution.

immer

Immer is a tiny package that allows you to work with immutable state in a more convenient way. It is based on the copy-on-write mechanism. The main difference from Redux is that Immer allows you to write code that looks like it's mutating state directly, without actually mutating the state.

README

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. The Redux core is tiny (2kB, including dependencies), and has a rich ecosystem of addons.

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.

Installation

Create a React Redux App

The recommended way to start new apps with React and Redux Toolkit is by using our official Redux Toolkit + TS template for Vite, or by creating a new Next.js project using Next's with-redux template.

Both of these already have Redux Toolkit and React-Redux configured appropriately for that build tool, and come with a small example app that demonstrates how to use several of Redux Toolkit's features.

# Vite with our Redux+TS template
# (using the `degit` tool to clone and extract the template)
npx degit reduxjs/redux-templates/packages/vite-template-redux my-app

# Next.js using the `with-redux` template
npx create-next-app --example with-redux my-app

We do not currently have official React Native templates, but recommend these templates for standard React Native and for Expo:

• https://github.com/rahsheen/react-native-template-redux-typescript
• https://github.com/rahsheen/expo-template-redux-typescript

npm install @reduxjs/toolkit react-redux

For the Redux core library by itself:

npm install redux

For more details, see the Installation docs page.

Documentation

The Redux core docs are located at https://redux.js.org, and include the full Redux tutorials, as well usage guides on general Redux patterns:

• Introduction
• Tutorials
• Usage Guides
• FAQ
• API Reference

The Redux Toolkit docs are available at https://redux-toolkit.js.org, including API references and usage guides for all of the APIs included in Redux Toolkit.

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.

Redux Fundamentals Tutorial

The Redux Fundamentals tutorial is a "bottom-up" tutorial that teaches "how Redux works" from first principles and without any abstractions, and why standard Redux usage patterns exist.

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 - please come and join us there!

Before Proceeding Further

Redux is a valuable tool for organizing your state, but you should also consider whether it's appropriate for your situation. Please don't use Redux just because someone said you should - instead, please 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 a 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, please see:

• When (and when not) to reach for 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

Basic Example

The whole global state of your app is stored in an object tree inside a single store. The only way to change the state tree is to create an action, an object describing what happened, and dispatch it to the store. To specify how state gets updated in response to an action, you write pure reducer functions that calculate a new state based on the old state and the action.

Redux Toolkit simplifies the process of writing Redux logic and setting up the store. With Redux Toolkit, the basic app logic looks like:

import { createSlice, configureStore } from '@reduxjs/toolkit'

const counterSlice = createSlice({
  name: 'counter',
  initialState: {
    value: 0
  },
  reducers: {
    incremented: state => {
      // Redux Toolkit allows us to write "mutating" logic in reducers. It
      // doesn't actually mutate the state because it uses the Immer library,
      // which detects changes to a "draft state" and produces a brand new
      // immutable state based off those changes
      state.value += 1
    },
    decremented: state => {
      state.value -= 1
    }
  }
})

export const { incremented, decremented } = counterSlice.actions

const store = configureStore({
  reducer: counterSlice.reducer
})

// Can still subscribe to the store
store.subscribe(() => console.log(store.getState()))

// Still pass action objects to `dispatch`, but they're created for us
store.dispatch(incremented())
// {value: 1}
store.dispatch(incremented())
// {value: 2}
store.dispatch(decremented())
// {value: 1}

Redux Toolkit allows us to write shorter logic that's easier to read, while still following the original core Redux behavior and data flow.

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.

License

MIT