Redux
Predictable State Container for JavaScript Apps, which behave consistently, run in different environments (client, server, and native), and easy to test
React 之類的函式庫，試著從 View Layer 處理 Mutation 與 Asynchronicity 的複雜問題，但它們把 Data State 的管理機制留給開發者決定，這便是 Redux 想要的切入點。先前的 Flux, CQRS, Event Sourcing 有處理過這種問題，Redux 對於更新提出限制，讓 State Mutation 變得可預測。 同類產品及使用時機
Redux Persist migrating States get-started-with-gatsby-2-and-redux advanced-redux-patterns-selectors
Before Hooks, functional components had no state. Now, with the useState(), we can do it.
https://medium.com/@tindleaj/understand-array-map-in-javascript-by-rolling-your-own-842d6031f168 how-does-redux-work