React as Front-end and Node as Back-end

First Method:

Set up react’s package.json that proxies non text/html requests through to an alternative back end.

Example post:

https://www.twilio.com/blog/react-app-with-node-js-server-proxy

Second Method:

Add cors(cross-origin resource sharing) to nodejs

https://www.npmjs.com/package/cors

Example blog:

How to create a React frontend and a Node/Express backend and connect them