title: How can I determine if my React Native app is a debug or release build from JavaScript code?
body: <p>I'd like to add some debug-only UI to my React Native app, but I can't find any equivalent of <code>RCT_DEBUG</code> or <code>RCT_DEV</code> compile-time flags in the JavaScript environment. Is there one?</p>
  
  <p>Use case: I want to add a status bar that shows the number of HTTP requests initiated by my app. Obviously this is not part of a shipping app, but it would help me check my work while in development and testing.</p>