At the moment when developing a Web app for the desktop (that is not on an Android device) the only way to debug is to start the Web runtime with the Error console .
This request is thus:
When running the Web runtime from the command line the console methods  should output to stdout.
 : https://developer.mozilla.org/en-US/docs/Apps/Tutorials/Debugging_the_app
 : https://developer.mozilla.org/en-US/docs/DOM/console
We could override the console object and log to stdout, if we want this.
We will support a developer mode with console, debugger and all the tools available in Firefox.