You can use these API calls in your code if you need to, but I've actually found them quite useful when on the console in Chrome:
require.defined(moduleId)
- returns true if your moduleId has been defined and is ready for use.
require.specified(moduleId)
- returns true if your moduleId has been listed as a dependency by another defined module. Note that just because this returns true doesn't mean your moduleId is ready to use (don't you just love asynchrony?).
requirejs.s.contexts._.config
- I learned about this from Vernon Kesner. This is technically a "back door/undocumented" call - so it could change or disappear without warning. However it returns a very useful object full of configuration info, see below:
Chrome Console results for requrejs.s.conects._.config