Proper encoding headers need to be set when requesting and serving the resource e.g. Content-Type and Content-Encoding. Just having utf-8 charset doesn't mean the content is not encoded in some other encoding. Inspect the requested .js file in a unicode aware text editor and see if it really is unicode encoded or just platform default encoded data served with a unicode encoding.
Encoding related issues mostly revolve around incorrect encoding used when serving data or having data which isn't utf encoded and being served as unicode.
~s.o.s~
Failure as a human
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