Gain insights into Redux, an open-source library for managing app state. Learn about Redux store creation, middleware, state management, error handling, testing, and building robust applications.

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Redux

In this course, you will take a deep dive into Redux, an open-source JavaScript library for managing application state.

You will start by running through what Redux is, general concepts, and basic implementation. With the basics out of the way, you will begin working on building a recipe book application, adding more bells and whistles to it as the course progresses. You will learn to create a Redux store, how to work with middleware, state management, error handling, testing, and a whole lot more.

By the end, you will have advanced knowledge of one the most popular libraries among React and Angular developers. You will have the skills to create highly performant and consistent.

The Ultimate Guide to Redux


One of the best-known store enhancers is `applyMiddleware()`. This is currently the only store enhancer provided by Redux. The redux code in the library is as follows:


~~~~~~~
export default function applyMiddleware(...middlewares) {
  return (createStore) => (reducer, preloadedState, enhancer) => {
    var store = createStore(reducer, preloadedState, enhancer)
    var dispatch = store.dispatch
    var chain = []

    var middlewareAPI = {
      getState: store.getState,
      dispatch: (action) => dispatch(action)
    }
    chain = middlewares.map(middleware => middleware(middlewareAPI))
    dispatch = compose(...chain)(store.dispatch)

    return { ...store, dispatch }
  }
}
~~~~~~~


At its core, `applyMiddleware()` changes the store’s default `dispatch()` method to pass the action through the chain of middleware provided by the user:


~~~~~~~
var store = createStore(reducer, preloadedState, enhancer)
var dispatch = store.dispatch
var chain = []

var middlewareAPI = {
  getState: store.getState,
  dispatch: (action) => dispatch(action)
}
~~~~~~~

First, a store is created, and the core `getState()` and `dispatch()` methods are wrapped in `middlewareAPI`. This is the object our middleware receives as the first parameter.

~~~~~~~
chain = middlewares.map(middleware => middleware(middlewareAPI))
~~~~~~~

The array of middleware is transformed into  calling `middleware()` with `middlewareAPI` as its argument. This essentially passes the `middlewareAPI` through all the middleware that the user has specified.

The last stage is to use the `compose()` function to decorate the middleware one after another:


~~~~~~~
dispatch = compose(...chain)(store.dispatch)
~~~~~~~

This line causes each middleware to decorate the chain of previous ones in a fashion similar to this:


~~~~~~~
middlewareA(middlewareB(middlewareC(store.dispatch)));
~~~~~~~

The original `store.dispatch()` passes as a parameter to the first wrapper in the chain.



Learn about the applyMiddleware function.

Introduction to Redux

Basic Redux Implementation

Cloning a Redux Boilerplate

Complete Redux Project

Creating a Store

Decorating the Store

Actions and Action Creators

Redux Thunk

Redux-Actions Library

Reducers

Avoiding Mutations

Introduction to Middleware

Your First Middleware

Middleware

State Management

Keeping a Normalized State

Persistence State

Real-World State

Server Communication

Moving Code from Action Creators

Error Handling

Server Communication II

Transforming Data

Chaining Requests

Managing Side Effects

Messaging Patterns

WebSockets

WebSocket Authentication

Testing

Testing Action Creators

Async Action Creators

Testing Reducers

Testing Middleware

Testing Async Middleware

Integration Tests

Evolution Of Redux

Final Assessment

The applyMiddleware function