What is the use of CDATA inside JavaScript tags and HTML?
<script type="text/javascript">
// <![CDATA[
// ]]>
</script>
This question is related to
javascript
html
xhtml
cdata
The answer is
A way to write a common subset of HTML and XHTML
In the hope of greater portability.
In HTML, <script> is magic escapes everything until </script> appears.
So you can write:
<script>x = '<br/>';
and <br/> won't be considered a tag.
This is why strings such as:
x = '</scripts>'
must be escaped like:
x = '</scri' + 'pts>'
See: Why split the <script> tag when writing it with document.write()?
But XML (and thus XHTML, which is a "subset" of XML, unlike HTML), doesn't have that magic: <br/> would be seen as a tag.
<![CDATA[ is the XHTML way to say:
don't parse any tags until the next
]]>, consider it all a string
The // is added to make the CDATA work well in HTML as well.
In HTML <![CDATA[ is not magic, so it would be run by JavaScript. So // is used to comment it out.
The XHTML also sees the //, but will observe it as an empty comment line which is not a problem:
//
That said:
- compliant browsers should recognize if the document is HTML or XHTML from the initial doctype
<!DOCTYPE html>vs<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> - compliant websites could rely on compliant browsers, and coordinate doctype with a single valid
scriptsyntax
But that violates the golden rule of the Internet:
don't trust third parties, or your product will break
From http://en.wikipedia.org/wiki/CDATA:
Since it is useful to be able to use less-than signs (<) and ampersands (&) in web page scripts, and to a lesser extent styles, without having to remember to escape them, it is common to use CDATA markers around the text of inline and elements in XHTML documents. But so that the document can also be parsed by HTML parsers, which do not recognise the CDATA markers, the CDATA markers are usually commented-out, as in this JavaScript example:
<script type="text/javascript">
//<![CDATA[
document.write("<");
//]]>
</script>
CDATA is Obsolete.
Note that CDATA sections should not be used within HTML; they only work in XML.
So do not use it in HTML 5.
https://developer.mozilla.org/en-US/docs/Web/API/CDATASection#Specifications
CDATA is a sequence of characters from the document character set and may include character entities. User agents should interpret attribute values as follows: Replace character entities with characters,
Ignore line feeds,
Replace each carriage return or tab with a single space.
CDATA has no meaning at all in HTML.
CDATA is an XML construct which sets a tag's contents that is normally #PCDATA - parsed character data, to be instead taken as #CDATA, that is, non-parsed character data. It is only relevant and valid in XHTML.
It is used in script tags to avoid parsing < and &. In HTML, this is not needed, because in HTML, script is already #CDATA.
Source: Stackoverflow.com