Html Script Tag: Type or Language (Or Omit Both)

HTML Script tag: type or language (or omit both)?

The language attribute has been deprecated for a long time, and should not be used.

When W3C was working on HTML5, they discovered all browsers have "text/javascript" as the default script type, so they standardized it to be the default value. Hence, you don't need type either.

For pages in XHTML 1.0 or HTML 4.01 omitting type is considered invalid. Try validating the following:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<script src="http://example.com/test.js"></script>
</head>
<body/>
</html>

You will be informed of the following error:

Line 4, Column 41: required attribute "type" not specified

So if you're a fan of standards, use it. It should have no practical effect, but, when in doubt, may as well go by the spec.

language=javascript vs. type=text/javascript

<script language="javascript"> was used in very old browsers, and is deprecated.

<script type="text/javascript"> is the HTML 4 standard.

In HTML 5, the type parameter is optional (text/javascript is the default), so you can just do <script>.

As a neat hack, if you put an invalid type, the script won't be ran, but you can still read the data in JavaScript. Some template libraries do this.

script tag vs script type = 'text/javascript' tag

In HTML 4, the type attribute is required. In my experience, all
browsers will default to text/javascript if it is absent, but that
behaviour is not defined anywhere. While you can in theory leave it
out and assume it will be interpreted as JavaScript, it's invalid
HTML, so why not add it.

In HTML 5, the type attribute is optional and defaults to
text/javascript

Use <script type="text/javascript"> or simply <script> (if omitted, the type is the same). Do not use <script language="JavaScript">; the language attribute is deprecated

Ref :

http://social.msdn.microsoft.com/Forums/vstudio/en-US/65aaf5f3-09db-4f7e-a32d-d53e9720ad4c/script-languagejavascript-or-script-typetextjavascript-?forum=netfxjscript

and

Difference between <script> tag with type and <script> without type?

Do you need type attribute at all?

I am using HTML5- No

I am not using HTML5 - Yes

Difference between script type and script language declarations

Use <script type="text/javascript"> or simply <script> (if omitted, the type is the same). Do not use <script language="JavaScript">; the language attribute is deprecated.

Not stating the script language when using Javascript

In Firefox, language is deprecated (so you shouldn't use it at all) and if you don't specify type, it will be assumed to be JavaScript.

type

This attribute identifies the scripting language of code embedded within a script element or referenced via the element’s src attribute.
This is specified as a MIME type; examples of supported MIME types
include text/javascript, text/ecmascript, application/javascript, and
application/ecmascript. If this attribute is absent, the script is
treated as JavaScript.

language Deprecated

Like the type attribute, this attribute identifies the scripting language in use. Unlike the type attribute, however, this attribute’s
possible values were never standardized. The type attribute should be
used instead.

The recommendation seems to be to include a type, but I doubt it has any performance impact since JavaScript is the only supported type. It's possible that it puts some browsers into quirks mode though, which would be very bad.

Should I include type=text/javascript in my SCRIPT tags?

You misunderstood what Crockford meant, he didn't say the type attribute is completely invalid, it's just that it's incorrect. The MIME type for JavaScript is application/javascript (or application/ecmascript I can't remember right now).

The general usage though is that is text/javascript which browsers will handle without any problems as that's been the defacto standard for a long time.

In regards to the <script src="..." tag it is redundant because the server determines the MIME type of the file and that is what the browser will then deal with.

He best explains it in one of his videos on YUI Theater (http://developer.yahoo.com/yui/theater/). I don't remember exactly which one he talks about this, I think it was in the advanced JavaScript series (but yeah I've watched them all a few times so they kind of blur into each other).

So if you want to write valid XHTML you need to provide something like text/javascript but it's not the official MIME type of the JavaScript language.

Leaving out type=text/javascript language=javascript

I suppose this should be updated now that the landscape has changed quite a bit:

For an HTML5 doctype, it's no longer required. For example: we leave it out of the pages here at Stack Overflow. If you're using an HTML5 doctype then it's completely optional and defaults to text/javascript, so you're absolutely fine leaving it off in every current (or even very old) browser. Realistically, this was also true even in HTML4 though not strictly valid HTML.

For an HTML4 doctype (to be valid), you need it. For a browser to actually function, it's not strictly needed and will behave just fine (this has been true all the way back to Netscape 2) - but it won't be valid HTML. If you have an HTML4 doctype, then keep it around and be valid - cause hey, why not?

Original Answer:

I would use type="text/javascript" to be safe in all current browsers, why leave the ambiguity in there to save 21 characters? language="" however is deprecated, I'd leave it out.

Also, any validator is going to throw an error, though it will likely work inside the browser (unless you're dealing with something very old).

What would the impact of not including a type in the script element be?

It is not a requirement as of HTML5. If type is left off, it is assumed to be JavaScript. You only need the type for other kinds of scripts. Non-JS based script tags are becoming more common. People often use them to store their client side templates.

For example in Angular, it's common to see script tags like <script type="text/ng-template" id="mytemplate.html">...</script>

Difference between script tag with type and script without type?

In HTML 4, the type attribute is required. In my experience, all browsers will default to text/javascript if it is absent, but that behaviour is not defined anywhere. While you can in theory leave it out and assume it will be interpreted as JavaScript, it's invalid HTML, so why not add it.

In HTML 5, the type attribute is optional and defaults to text/javascript:

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".

Is the 'type' attribute necessary for script tags?

For HTML 4.x, the type attribute is required. Source

This attribute specifies the scripting language of the element's contents and overrides the default scripting language. The scripting language is specified as a content type (e.g., "text/javascript"). Authors must supply a value for this attribute. There is no default value for this attribute.

For HTML 5, it is optional. If it is not specified, it defaults to text/javascript. Source

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".

Recommendation: See HTML 5.2

For HTML 5.2, it should be omitted if using a valid JavaScript MIME type (e.g. text/javascript). Source

Omitting the attribute, or setting it to a JavaScript MIME type, means that the script is a classic script, to be interpreted according to the JavaScript Script top-level production. Classic scripts are affected by the charset, async, and defer attributes. Authors should omit the attribute, instead of redundantly giving a JavaScript MIME type.

Html Script Tag: Type or Language (Or Omit Both)