From: es-discuss [mailto:es-discuss-boun...@mozilla.org] On Behalf Of Brendan 
Eich

> Examples? What is the specified grammar?

>From [the HTML spec][1]:

> The `type` attribute gives the language of the script or format of the data. 
> If the attribute is present, its value must be a [valid MIME type][2]. The 
> `charset` parameter must not be specified. The default, which is used if the 
> attribute is absent, is `"text/javascript"`.

Then there's a bunch of other text regarding how the `type` attribute 
translates into MIME types and how mime types end up translating to "supported 
scripting languages", ending up at [3].

---

My understanding of what's been specified here, codified from legacy, is that 
browsers (since the dawn of time) always interpreted either missing `type` 
attribute or "text/javascript" as instructions to execute JavaScript code, and 
most other things as inert and ignored.

There's a bit of a gray area involving all the other "aliases" for 
text/javascript, e.g. some older browsers probably don't support 
text/livescript, while others probably don't support text/jscript.

The upside is that, as Arv says, you can put any string you want in there, and 
browsers will cope just fine by ignoring it unless it's one of the specific 
types that maps to JavaScript per [3]. The spec has authoring conformance 
criteria that it must be a MIME type. But the actual codified behavior is 
closer to "if it's in this list of strings, or absent, you get JavaScript; 
otherwise it gets ignored, unless the browser wants to implement 
VBScript/Dart/etc. using some other magic string."

[1]: 
http://www.whatwg.org/specs/web-apps/current-work/multipage/scripting-1.html#the-script-element
[2]: 
http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#valid-mime-type
[3]: 
http://www.whatwg.org/specs/web-apps/current-work/multipage/scripting-1.html#support-the-scripting-language

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