I'm currently developing an app using React Native (JavaScript). My client is running logcat through the SDK command like using this command (found on the official wiki):
adb logcat *:S ReactNative:V ReactNativeJS:V
This should show all level messages (console.trace all the way to console.error). However it does not show Debug or Trace messages. It shows every other message just fine. The messages show just fine on the React Native debugger, just not on Logcat.
Run by connecting a physical Android device to the computer and running the command. Unfortunately the client can not run an emulator (incompatible CPU) and can not run from source, so they can not use React Native's built-in debugger.