Pourquoi les éléments de script à fermeture automatique ne fonctionnent-ils pas?

StackOverflow https://stackoverflow.com/questions/69913

Question

Quelle est la raison pour laquelle les navigateurs ne reconnaissent pas correctement: 

<script src="foobar.js" /> <!-- self-closing script element -->

Seulement ceci est reconnu: 

<script src="foobar.js"></script>

Est-ce que cela rompt avec le concept de support XHTML?

Remarque: cette instruction est correcte au moins pour tous les IE (6-8 bêta 2).

Était-ce utile?

La solution

La spécification XHTML 1 dit:

& # 1057; .3. Minimisation des éléments et contenu des éléments vides

  

Étant donné qu'une instance vide d'un élément dont le modèle de contenu n'est pas EMPTY (par exemple, un titre ou un paragraphe vide), n'utilisez pas la forme réduite (par exemple, utilisez <p> </p> et non <p />).

La DTD XHTML spécifie les éléments de script sous la forme: 

<!-- script statements, which may include CDATA sections -->
<!ELEMENT script (#PCDATA)>

Autres conseils

Pour ajouter à ce que Brad et escadette ont dit, la syntaxe XML à fermeture automatique <script /> est le code XML correct, mais pour que cela fonctionne dans la pratique, votre serveur Web doit également envoyer votre message. les documents en tant que XML correctement formé avec un type MIME XML tel que application/xhtml+xml dans l'en-tête HTTP Content-Type (et pas comme text/html).

Cependant, l'envoi d'un type MIME XML fera que vos pages ne seront pas analysées par IE7, qui n'aime que <script></script>.

De w3 :

  

En résumé, 'application / xhtml + xml'   DEVRAIT être utilisé pour la famille XHTML   documents, et l'utilisation de 'text / html'   DEVRAIT être limité à compatible HTML   Documents XHTML 1.0. 'application / xml'   et 'text / xml' PEUVENT aussi être utilisés, mais   le cas échéant,   'application / xhtml + xml' DEVRAIT être utilisé   plutôt que les supports XML génériques   types.

Cela m'a déconcerté il y a quelques mois, et la seule solution utilisable (compatible avec FF3 + et IE7) consistait à utiliser l'ancienne syntaxe http-equiv avec <=> (syntaxe HTML + type MIME HTML).

Si votre serveur envoie le type <=> dans ses en-têtes HTTP, même avec des documents XHTML correctement formés, FF3 + utilisera son mode de rendu HTML, ce qui signifie que <=> ne fonctionnera pas (il s'agit d'un changement, Firefox était auparavant moins stricte).

Cela se produira quels que soient les manipulations avec <=> les méta-éléments, le prologue XML ou le type de document contenu dans votre document - Firefox se branche dès qu'il obtient l'en-tête <=> qui détermine si l'analyseur HTML ou XML recherche dans le document , et l'analyseur HTML ne comprend pas <=>.

Si vous êtes curieux, la raison ultime est que HTML était à l’origine un dialecte de SGML, qui est le grand frère étrange de XML. Dans SGML-land, les éléments peuvent être spécifiés dans la DTD comme étant à fermeture automatique (par exemple, BR, HR, INPUT), fermables de manière implicite (par exemple, P, LI, TD) ou explicitement fermables (par exemple, TABLE, DIV, SCRIPT). XML n’a bien sûr pas la moindre idée de cela.

Les analyseurs syntaxiques de balises utilisés par les navigateurs modernes sont issus de cet héritage, bien que leur modèle d'analyse syntaxique ne soit plus du pur SGML. Et bien sûr, votre XHTML soigneusement conçu est traité comme une balise-tag mal inspirée par SGML, à moins que vous ne l'envoyiez avec un type mime XML. C'est aussi pourquoi ... 

<p><div>hello</div></p>

... est interprété par le navigateur comme: 

<p></p><div>hello</div><p></p>

... qui est la recette d'un joli bogue obscur qui peut vous gêner lorsque vous essayez de coder contre le DOM.

Others have answered "how" and quoted spec. Here is the real story of "why no <script/>", after many hours digging into bug reports and mailing lists.

HTML 4

HTML 4 is based on SGML.

SGML has some shorttags, such as <BR//, <B>text</>, <B/text/, or <OL<LI>item</LI</OL>. XML takes the first form, redefines the ending as ">" (SGML is flexible), so that it becomes <BR/>.

However, HTML did not redfine, so <SCRIPT/> should mean <SCRIPT>>.
(Yes, the '>' should be part of content, and the tag is still not closed.)

Obviously, this is incompatible with XHTML and will break many sites (by the time browsers were mature enough to care about this), so nobody implemented shorttags and the specification advises against them.

Effectively, all 'working' self-ended tags are tags with optional end tag on technically non-conformant parsers and are in fact invalid. It was W3C which came up with this hack to help transitioning to XHTML by making it HTML-compatible.

And <script>'s end tag is not optional.

"Self-ending" tag is a hack in HTML 4 and is meaningless.

HTML 5

HTML5 has five types of tags and only 'void' and 'foreign' tags are allowed to be self-closing.

Because <script> is not void (it may have content) and is not foreign (like MathML or SVG), <script> cannot be self-closed, regardless of how you use it.

But why? Can't they regard it as foreign, make special case, or something?

HTML 5 aims to be backward-compatible with implementations of HTML 4 and XHTML 1. It is not based on SGML or XML; its syntax is mainly concerned with documenting and uniting the implementations. (This is why <br/> <hr/> etc. are valid HTML 5 despite being invalid HTML4.)

Self-closing <script> is one of the tags where implementations used to differ. It used to work in Chrome, Safari, and Opera; to my knowledge it never worked in Internet Explorer or Firefox.

This was discussed when HTML 5 was being drafted and got rejected because it breaks browser compatibility. Webpages that self-close script tag may not render correctly (if at all) in old browsers. There were other proposals, but they can't solve the compatibility problem either.

After the draft was released, WebKit updated the parser to be in conformance.

Self-closing <script> does not happen in HTML 5 because of backward compatibility to HTML 4 and XHTML 1.

XHTML 1 / XHTML 5

When really served as XHTML, <script/> is really closed, as other answers have stated.

Except that the spec says it should have worked when served as HTML:

XHTML Documents ... may be labeled with the Internet Media Type "text/html" [RFC2854], as they are compatible with most HTML browsers.

So, what happened?

People asked Mozilla to let Firefox parse conforming documents as XHTML regardless of the specified content header (known as content sniffing). This would have allowed self-closing scripts, and content sniffing was necessary anyway because web hosters were not mature enough to serve the correct header; IE was good at it.

If the first browser war didn't end with IE 6, XHTML may have been on the list, too. But it did end. And IE 6 has a problem with XHTML. In fact IE did not support the correct MIME type at all, forcing everyone to use text/html for XHTML because IE had major market share for a whole decade.

And also content sniffing can be really bad and people are saying it should be stopped.

Finally, it turns out that the W3C didn't mean XHTML to be sniffable: the document is both, HTML and XHTML, and Content-Type rules. One can say they were standing firm on "just follow our spec" and ignoring what was practical. A mistake that continued into later XHTML versions.

Anyway, this decision settled the matter for Firefox. It was 7 years before Chrome was born; there was no other significant browser. Thus it was decided.

Specifying the doctype alone does not trigger XML parsing because of following specifications.

Internet Explorer 8 and earlier do not support XHTML parsing. Even if you use an XML declaration and/or an XHTML doctype, old IE still parse the document as plain HTML. And in plain HTML, the self-closing syntax is not supported. The trailing slash is just ignored, you have to use an explicit closing tag.

Even browsers with support for XHTML parsing, such as IE 9 and later, will still parse the document as HTML unless you serve the document with a XML content type. But in that case old IE will not display the document at all!

The people above have already pretty much explained the issue, but one thing that might make things clear is that, though people use <br/> and such all the time in HTML documents, any / in such a position is basically ignored, and only used when trying to make something both parseable as XML and HTML. Try <p/>foo</p>, for example, and you get a regular paragraph.

The self closing script tag won't work, because the script tag can contain inline code, and HTML is not smart enough to turn on or off that feature based on the presence of an attribute.

On the other hand, HTML does have an excellent tag for including references to outside resources: the <link> tag, and it can be self-closing. It's already used to include stylesheets, RSS and Atom feeds, canonical URIs, and all sorts of other goodies. Why not JavaScript?

If you want the script tag to be self enclosed you can't do that as I said, but there is an alternative, though not a smart one. You can use the self closing link tag and link to your JavaScript by giving it a type of text/javascript and rel as script, something like below:

<link type="text/javascript" rel ="script" href="/path/tp/javascript" />

Unlike XML and XHTML, HTML has no knowledge of the self-closing syntax. Browsers that interpret XHTML as HTML don't know that the / character indicates that the tag should be self-closing; instead they interpret it like an empty attribute and the parser still thinks the tag is 'open'.

Just as <script defer> is treated as <script defer="defer">, <script /> is treated as <script /="/">.

Internet Explorer 8 and older don't support the proper MIME type for XHTML, application/xhtml+xml. If you're serving XHTML as text/html, which you have to for these older versions of Internet Explorer to do anything, it will be interpreted as HTML 4.01. You can only use the short syntax with any element that permits the closing tag to be omitted. See the HTML 4.01 Specification.

The XML 'short form' is interpreted as an attribute named /, which (because there is no equals sign) is interpreted as having an implicit value of "/". This is strictly wrong in HTML 4.01 - undeclared attributes are not permitted - but browsers will ignore it.

IE9 and later support XHTML 5 served with application/xhtml+xml.

That's because SCRIPT TAG is not a VOID ELEMENT.

In an HTML Document - VOID ELEMENTS do not need a "closing tag" at all!

In xhtml, everything is Generic, therefore they all need termination e.g. a "closing tag"; Including br, a simple line-break, as <br></br> or its shorthand <br />.

However, a Script Element is never a void or a parametric Element, because script tag before anything else, is a Browser Instruction, not a Data Description declaration.

Principally, a Semantic Termination Instruction e.g., a "closing tag" is only needed for processing instructions who's semantics cannot be terminated by a succeeding tag. For instance:

<H1> semantics cannot be terminated by a following <P> because it doesn't carry enough of its own semantics to override and therefore terminate the previous H1 instruction set. Although it will be able to break the stream into a new paragraph line, it is not "strong enough" to override the present font size & style line-height pouring down the stream, i.e leaking from H1 (because P doesn't have it).

This is how and why the "/" (termination) signalling has been invented.

A generic no-description termination Tag like < />, would have sufficed for any single fall off the encountered cascade, e.g.: <H1>Title< /> but that's not always the case, because we also want to be capable of "nesting", multiple intermediary tagging of the Stream: split into torrents before wrapping / falling onto another cascade. As a consequence a generic terminator such as < /> would not be able to determine the target of a property to terminate. For example: <b>bold <i>bold-italic < /> italic </>normal. Would undoubtedly fail to get our intention right and would most probably interpret it as bold bold-itallic bold normal.

This is how the notion of a wrapper ie., container was born. (These notions are so similar that it is impossible to discern and sometimes the same element may have both. <H1> is both wrapper and container at the same time. Whereas <B> only a semantic wrapper). We'll need a plain, no semantics container. And of course the invention of a DIV Element came by.

The DIV element is actually a 2BR-Container. Of course the coming of CSS made the whole situation weirder than it would otherwise have been and caused a great confusion with many great consequences - indirectly!

Because with CSS you could easily override the native pre&after BR behavior of a newly invented DIV, it is often referred to, as a "do nothing container". Which is, naturally wrong! DIVs are block elements and will natively break the line of the stream both before and after the end signalling. Soon the WEB started suffering from page DIV-itis. Most of them still are.

The coming of CSS with its capability to fully override and completely redefine the native behavior of any HTML Tag, somehow managed to confuse and blur the whole meaning of HTML existence...

Suddenly all HTML tags appeared as if obsolete, they were defaced, stripped of all their original meaning, identity and purpose. Somehow you'd gain the impression that they're no longer needed. Saying: A single container-wrapper tag would suffice for all the data presentation. Just add the required attributes. Why not have meaningful tags instead; Invent tag names as you go and let the CSS bother with the rest.

This is how xhtml was born and of course the great blunt, paid so dearly by new comers and a distorted vision of what is what, and what's the damn purpose of it all. W3C went from World Wide Web to What Went Wrong, Comrades?!!

The purpose of HTML is to stream meaningful data to the human recipient.

To deliver Information.

The formal part is there to only assist the clarity of information delivery. xhtml doesn't give the slightest consideration to the information. - To it, the information is absolutely irrelevant.

The most important thing in the matter is to know and be able to understand that xhtml is not just a version of some extended HTML, xhtml is a completely different beast; grounds up; and therefore it is wise to keep them separate.

Difference between 'true XHTML', 'faux XHTML' and HTML as well as importance of the server-sent MIME type had been already described here well. If you want to try it out right now, here is simple editable snippet with live preview including self-closed script tag for capable browsers:

div { display: flex; }
div + div {flex-direction: column; }
<div>Mime type: <label><input type="radio" onchange="t.onkeyup()" id="x" checked  name="mime"> application/xhtml+xml</label>
<label><input type="radio" onchange="t.onkeyup()" name="mime"> text/html</label></div>
<div><textarea id="t" rows="4" 
onkeyup="i.src='data:'+(x.checked?'application/xhtml+xml':'text/html')+','+encodeURIComponent(t.value)"
><?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"
[<!ENTITY x "true XHTML">]>
<html xmlns="http://www.w3.org/1999/xhtml">
<body>
  <p>
    <span id="greet" swapto="Hello">Hell, NO :(</span> &x;.
    <script src="data:text/javascript,(g=document.getElementById('greet')).innerText=g.getAttribute('swapto')" />
    Nice to meet you!
    <!-- 
      Previous text node and all further content falls into SCRIPT element content in text/html mode, so is not rendered. Because no end script tag is found, no script runs in text/html
    -->
  </p>
</body>
</html></textarea>

<iframe id="i" height="80"></iframe>

<script>t.onkeyup()</script>
</div>

You should see Hello, true XHTML. Nice to meet you! below textarea.

For incapable browsers you can copy content of the textarea and save it as a file with .xhtml (or .xht) extension (thanks Alek for this hint).

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