Intro to Redux.js

2020-03-16   2 min read

RoboRedux demo

GitHub repo

(1) What is Redux and when to use it?

Redux manages the state, so it's userful when your application is large and you need to manage many states and share them between multiple containers.

(2) Three Redux principles

1. Single source of truth - bundle state in one object store

You'd have one single object store that describes the entire state of the app.

2. state is ready only

Instead of updating a state, in Redux you create a new state every time state changes, like below

example of creatting a new state instead of modifying it

This encourages immutabililty and prevents unexpected errors.

3. Pure functions

Changes are taken care of by pure functions called reducers in Redux.

(3) How Redux works

1. Actions (+ middleware)

Actions such as 'click a submit button' or 'fetch API call' need to be registred as action and dispatched to be triggered.


2. Reducers

Reducers are pure functions that takes actions and spit out store(= this.state). They process actions and create a new state based on them.

example of reducer

3. Store

store is basically this.state in Redux. It's an object that describes state of the whole application. You pass this down to <App /> as a prop. Reducers take actions and return state, which gets passed to store. how to declare store

4. Changes happen

Once store is updated, React detects the change(s) and updates the view layer. These 4 stages happen only from action to view layer update, which is called a uni-directional data flow.

Typos/comments/suggestions are welcomed on GitHub issues


Made with Bulma