Is the 'Type' Attribute Necessary For ≪Script≫ Tags

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.

Do HTML5 Script tag need type= javascript ?

No, it's now officially useless.

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".

Simply do

<script src=yourpath.js></script>

(yes, you can omit the quotes too)

Note that you don't have to worry about pre-HTML5 browsers, all of them always considered JavaScript to be the default script language.

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.

Do you need text/javascript specified in your script tags?

See Crockford's write-up on the <script> tag, most notably:

Do not use the <!-- //--> hack with scripts. It was intended to prevent scripts from showing up as text on the first generation browsers Netscape 1 and Mosaic. It has not been necessary for many years. <!-- //--> is supposed to signal an HTML comment. Comments should be ignored, not compiled and executed. Also, HTML comments are not to include --, so a script that decrements has an HTML error.

...

type="text/javascript"

This attribute is optional. Since Netscape 2, the default programming language in all browsers has been JavaScript. In XHTML, this attribute is required and unnecessary. In HTML, it is better to leave it out. The browser knows what to do.

Understanding the type attribute in a script tag

I want to understand the magic behind adding type='text/babel' to a script tag.

No real magic: The Babel script you include on the page looks for those elements and transpiles them into ES5 on-the-fly, then has the browser run the resulting ES5 code. Setting that type on the script elements does two things:

1. Prevents the browser from trying to run them directly, and

2. Identifies them for the Babel script.

Regarding type on script in general, from the specification:

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".

Then later when explaining how to process script elements:

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.

It's worth calling out what the Babel website says about transpiling in the browser:

Compiling in the browser has a fairly limited use case, so if you are working on a production site you should be precompiling your scripts server-side. See setup build systems for more information.

(Where they've said "compiling" most of us would say "transpiling.")

Do you really need to specify the type attribute?

Most people are used to HTML 4/XHTML and before, where the type attribute is required for these elements.

In regards to HTML 5, these are indeed optional and the spec gives a default, depending on the element.

For the script tag, this defaults to text/javascript:

If the language is not that described by "text/javascript", then the type attribute must be present

For the style tag, this defaults to text/css:

The default value for the type attribute, which is used if the attribute is absent, is "text/css".

So, not needed, as you stated. However, browser support and server setups can't always be relied on - being explicit is a good idea as it avoids such problems.

And of course, not all browsers out there support HTML 5 - those that don't will use an earlier version where the attribute is required and your javascript/css might not get parsed in such browsers, meaning you end up with no CSS or javascript on older browsers, when a simple solution for backwards compatibility is to add the attribute.

What is the difference between lang and type attributes in a script tag?

Per the HTML 4.01 Spec:

type:
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.

language: Deprecated. This attribute specifies the scripting language of the contents of this element. Its value is an identifier for the language, but since these identifiers are not standard, this attribute has been deprecated in favor of type.

Are Type Attributes on SCRIPT, STYLE, and LINK elements still needed?

In short, they are not required since HTML5, but are required by W3C standards in HTML4/XHTML.

In HTML5 type of script tag:

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.

in HTML4 and XHTML it's required by W3C standards.

For style and link type:

In HTML5, the type attribute is no longer required. Default value is
"text/css".

Enable script tags with different type? Changing type attribute is not enought

Yes you can do it, but your only option is recreate new script tag and remove existing:

$(document).ready(function() {    $('script[type=jquery]').each(function(){        $(this).after(this.outerHTML.replace('jquery','text/javascript')).remove();    })});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script type="jquery">alert('WORKING!')</script>