The GitHub language detection is based on linguist (as I described in this answer).
- The list of file extension analyzed is in
lib/linguist/languages.yml
- The list of files ignored is in
lib/linguist/vendor.yml
In your case, your js/css/json files could be:
too small to trigger that analysis- or too recent for that analysis to be completed
I suggest to wait another day before raising a ticket to GitHub support.
Update a few hours later: I suspect the language stats are only updated once a day, as they now are present on the OP's GitHub repo:
This is still the case in 2017, with pchaigno's comment:
(Paul Chaignon is one of the main contributors on the linguist project)
The language detection job (Linguist) is actually running as a background, low-priority job.
So it may take some time to update. Can be a few minutes, or a day.
You can see an example in "Paths not excluded from Github language statistics", where Paul suggests a way to debug how linguist applies to your repo.