Caution:
This page describes experimental features that are not yet available in a stable release. Don’t rely on experimental builds of React in production apps. These features may change significantly and without a warning before they become a part of React.
This documentation is aimed at early adopters and people who are curious. If you’re new to React, don’t worry about these features — you don’t need to learn them right now. For example, if you’re looking for a data fetching tutorial that works today, read this article instead.
React 16.6 added a component that lets you “wait” for some code to load and declaratively specify a loading state (like a spinner) while we’re waiting:
https://reactjs.org/docs/concurrent-mode-suspense.html - source! Express
