http://www.w3.org/TR/2014/REC-html5-20141028/scripting-1.html#attr-script-type
（1）type attribute
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. The charset parameter must not be specified. The default, which is used if the attribute is absent, is "text/javascript".
（2）script block's type
If either:
the script element has a type attribute and its value is the empty string, or
the script element has no type attribute but it has a language attribute and that attribute's value is the empty string, or
the script element has neither a type attribute nor a language attribute, then
...let the script block's type for this script element be "text/javascript".
Otherwise, if the script element has a type attribute, let the script block's type for this script element be the value of that attribute with any leading or trailing sequences of space characters removed.
Otherwise, the element has a non-empty language attribute; let the script block's type for this script element be the concatenation of the string "text/" followed by the value of the language attribute.
The language attribute is never conforming, and is always ignored if there is a type attribute present.
（3）scripting language
If the user agent does not support the scripting language given by the script block's type for this script element, then the user agent must abort these steps at this point. The script is not executed.
其中：
（1）valid MIME TYPE
http://www.w3.org/TR/2014/REC-html5-20141028/infrastructure.html#valid-mime-type
The term MIME type is used to refer to what is sometimes called an Internet media type in protocol literature. The term media type in this specification is used to refer to the type of media intended for presentation, as used by the CSS specifications.
A string is a valid MIME type if it matches the media-type rule defined in section 3.1.1.1 "Media Types" of RFC 7231. In particular, a valid MIME type may include MIME type parameters.
（2）Media Type
http://tools.ietf.org/html/rfc7231#section-3.1.1
3.1.1.1. Media Type
HTTP uses Internet media types [RFC2046] in the Content-Type
(Section 3.1.1.5) and Accept (Section 5.3.2) header fields in order
to provide open and extensible data typing and type negotiation.
Media types define both a data format and various processing models:
how to process that data in accordance with each context in which it
is received.
media-type = type "/" subtype *( OWS ";" OWS parameter )
type = token
subtype = token
The type/subtype MAY be followed by parameters in the form of
name=value pairs.
parameter = token "=" ( token / quoted-string )
The type, subtype, and parameter name tokens are case-insensitive.
Parameter values might or might not be case-sensitive, depending on
the semantics of the parameter name. The presence or absence of a
parameter might be significant to the processing of a media-type,
depending on its definition within the media type registry.
A parameter value that matches the token production can be
transmitted either as a token or within a quoted-string. The quoted
and unquoted values are equivalent. For example, the following
examples are all equivalent, but the first is preferred for
consistency:
text/html;charset=utf-8
text/html;charset=UTF-8
Text/HTML;Charset="utf-8"
text/html; charset="utf-8"
Internet media types ought to be registered with IANA according to
the procedures defined in [BCP13].
Note: Unlike some similar constructs in other header fields, media
type parameters do not allow whitespace (even "bad" whitespace)
around the "=" character.