Yup i wrote this demo in js last year since there was only a C# sharp demo. There are actually 2 repos and it makes sense from the backend. Can also use nip42 auth afaik.

GitHub
GitHub - bitkarrot/NIP98-js-client: NIP98 client demo in vanilla js (API auth in another repo)
NIP98 client demo in vanilla js (API auth in another repo) - bitkarrot/NIP98-js-client