Responsible JavaScript

Modern component-based frameworks (e.g., React) can render component markup not only on the client but also on a JavaScript backend as a string. This makes it possible to use the same component code on both the client and the server, which is an improvement for both the user and developer experiences. Don’t get complacent, though—server rendering is typically a synchronous and computationally expensive process. You’ll need to explore things like component caching in large apps to avoid inflating server response times