charset is not invalid in text/javascript MIME

[peter-lyons-kehl]

https://github.com/mdn/content/blob/main/files/en-us/web/http/guides/mime_types/index.md, rendered as https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types, is incorrect in part textjavascript:

"Per the IANA Media Types registry, RFC 9239, and the HTML specification, JavaScript content should always be served using the MIME type text/javascript. No other MIME types are considered valid for JavaScript, and using any MIME type other than text/javascript may result in scripts that do not load or run.

You may find some JavaScript content incorrectly served with a charset parameter as part of the MIME type — as an attempt to specify the character set for the script content. That charset parameter isn't valid for JavaScript content, and in most cases will result in a script failing to load."

The three links above (in the respective order):

• IANA Media Types registry > the only occurrence of text/javascript links to https://www.iana.org/assignments/media-types/text/javascript, which reads: "Optional parameters: charset."

• RFC 9239 > "The charset parameter is only used when processing a Script goal source; Module goal sources MUST always be processed as UTF-8." (bold formatting is mine)

• HTML specification > (the rest of this list item is one consecutive quote) > For external JavaScript resources, MIME type parameters in Content-Type headers are generally ignored. (In some cases the charset parameter has an effect.) However, for the script element's type attribute they are significant; it uses the JavaScript MIME type essence match concept.

  For example, scripts with their type attribute set to "text/javascript; charset=utf-8" will not be evaluated, even though that is a valid JavaScript MIME type when parsed.

  • that means "type attribute" of a <script type="..."> tag in HTML source. Specifically, "their type" links to HTML definition of type attribute of <script> element. NOT MIME as served by web server (or as specified in data: URLs).

I'm willing to provide a pull request.

[Josh-Cena]

Yes, it appears that this paragraph is talking about type in <script>, not Content-Type. PRs welcome.