That's all totally awesome and cool, right up until the moment you want to add a comment to your configuration. Because you know, it's configuration, and that requires comments.

Quite a few tools went from just JSON configuration files to supporting both .js and .json.

Regarding caching, perhaps I'm mistaken but what's the issue there? Two JSON documents can be equivalent with different bytes so you need to re-parse the configuration file fairly often anyway. So what's the difference with just re-evaluating a .js configuration file and caching the output? If someone wants to put a `if (random() > 0.1)` statement in their config then that's their problem.