title: React/Next.js recommended way to set constants such as backend API URLs
body: <p>I am looking through <code>next.js</code> documentation and trying to understand what the suggested approach is for setting URLs that change in different environments. Mostly, I want to ensure that I'm pointing backend URLs correctly in development versus production.</p>
  
  <p>I suppose you can create a constants configuration file, but is there a supported, best practice for this? </p>