I added a feature to uglifyjs for precisely this sort of "production" use -
in this way I use uglifyjs in a way similar to the C preprocessor to
entirely remove code blocks by telling uglifyjs it should consider certain
symbols to have specific defined values, and then using the inherent "dead
code removal" feature.

  https://github.com/mishoo/UglifyJS#use-as-a-code-pre-processor

In particular, my "un-uglified code" includes

 if (typeof DEVELOPMENT === "undefined") DEVELOPMENT = true;
 if (typeof PRODUCTION === "undefined") PRODUCTION = false;

This way, in development, I can have things like

  if (DEVELOPMENT) {
    Logger.configure([
    {context: 'nike.profile.core.Application', level: Logger.LOG, save:
true},
    {context: 'nike.profile.models.Account', level: Logger.WARN, save:
true},
    {context: 'nike.profile.models.User', level: Logger.INFO, save: true}
    ]);
  }

and then, when I uglify my code with command lines args "--define
PRODUCTION=true --define DEVELOPMENT=false" (in addition to any others)
then the entire block will be removed (including the 'if' test itself).

I don't really need both symbols, but it sometimes makes my intent clearer.

I also use this for setting certain flags or initialising values in
debug/production mode etc

Cheers

--
Tim