There's a good chance that your application will need to talk to API endpoints that are out of your control, for example, an application that is composed from many different microservice endpoints. It's rare that you can use data from these services without modification. Rather, you have to write code that transforms data so that it's usable by your React components.

If you're rendering your components on a Node.js server, then this data transformation code will be used by both the client and the server, because on the initial load, the server will need to talk to the API, and later on, the component in the browser will need to talk to the API.

It's not just about transforming the data that's returned from these services either. For example, you have to think about providing input to them as well, like when creating or modifying resources.

The fundamental adjustment that you'll need to make as a React programmer is to assume that any given component that you implement will need to be rendered on the server. This may seem like a minor adjustment, but the devil is in the detail. Speaking of which, let's jump into some code examples now.