RFC4329 and IANA says it's application/javascript, and text/javascript is obsolete. However, HTML standard (by WHATWG) says servers should use text/javascript rather than other obsolete types.
Why is there such a difference? What is the correct MIME type we should use for javascripts? Does it mean that web servers should use text/javascript for scripts meant to be run by the browsers and use application/javascript in other cases (e.g. for a js file to be downloaded)?
Not totally sure what was the historical reason when such decision has been made. Anyway, the latest RFC 9239 and IANA both suggest that text/javascript be the canonical MIME type for .js files.