Should I use a type attribute on script tags?
I have immense respect for Douglas Crockford, but that doesn't mean I can't disagree with him... Douglas has written on a number of occasions that he prefers plain script tags, with no attributes. The argument goes like this:
"This script block uses the
languageattribute. This was a feature that was introduced by Microsoft in order to support VBScript. Netscape then adopted it to support its own nonstandard deviations. W3C did not adopt thelanguageattribute, favoring instead atypeattribute which takes a MIME type. Unfortunately, the MIME type was not standardized, so it is sometimes"text/javascript"or"application/ecmascript"or something else. Fortunately, all browsers will always choose JavaScript as the default programming language, so it is always best to simply write<script>. It is smallest, and it works on the most browsers."
What he forgets to mention here is that if you care about XHTML compliance, you can't make the economy of the type attribute. I also think it's good practice as we don't know if in the future browsers won't support other scripting languages, even if the default will probably always remain JavaScript (and even if browsers don't support them, we've used our own type in the past for xml-script and handled the parsing ourselves). It's also more expressive.
The second thing that I think is not quite true here is that the MIME type wasn't standardized. MIME types are standardized by IANA (Internet Assigned Numbers Authority). IANA lists both "text/javascript" and "text/ecmascript" as obsolete, pointing to RFC 4329. The valid types are "application/javascript" and "application/ecmascript". All modern JavaScript interpreters being implementations of ECMAScript, it seems like it would be best to use "application/ecmascript".
Except that our good friend IE doesn't recognize them and ignores the script altogether if you use them. So once again, thanks to one more non-standard behavior of IE, we can't afford to follow the standard.
So to sum this up, if you don't care about XHTML compliance or expressiveness of your markup, it's probably safe to use a plain script tag. If you do, you should use "text/javascript" until IE gets its act together (if that ever happens).