Shouldn't a CDN be returning application/javascript as the content type for an asset like this?pic.twitter.com/UvnUOSSI69
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What do you mean? The browser has to decode the response somehow — there’s always a “default charset”.
text/ implies iso-8859-1 unless a charset= is provided in Content-Type, whereas application/ would sniff the charset. At least in theory (per RFCs); of course, in practice (WHATWG), it doesn't actually matter…
IOW, forget what I said 
I think RFCs acknowledged by now that’s bogus too, al least as far HTTP is concerned.
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