move api to new version and add tests

Yup, I totally agreed with you, and
> a project that uses JSON to manage its constants
 
I don't know, the few projects means hardly, such that i can not provide a module/package/project that use the JSON format to deploy their constants.

> "node itself use a js file to do this"?

Yes, see https://github.com/joyent/node/blob/master/src/node_constants.cc, even though it is a `.cc` format file, the stuffs what it did also is exporting certain number of constants in v8(js object).