Tag: cdata

Using comments to ‘hide’ SCRIPT tag content – please stop this obsolete practice

Many years ago, when HTML3 and 4 were still widely used in the mid to late 1990s, it was a common practice to place HTML style comments, or in some cases CDATA comments inside the SCRIPT tag in an attempt to hide that content from browsers that could not process it. In those browsers the content (javascript source code) would sometimes be displayed on the page, making it quite a mess.

This practice is now obsolete, and often problematic as there are very few of those browsers in use today – primarily only for testing of legacy functionality.

Example of old approach

<script type="text/javascript">
<--
// some script
-->
</script>

NOTE: for XHTML or XML documents, the use of a CDATA style comment is still required.
<script type=”text/javascript”>
//<![CDATA[
…code…
//]]>
</script>

REFERENCES:

CDATA markup of XHTML script and style tags

Ideally all JavaScript and CSS definitions should be external to the content of an HTML page, in some cases it’s simply not practical. If you’ve migrated to XHTML markup of your page, this can often lead to XML validation errors. The use of a CDATA escape can fix most issues, though you may have to cleanup some of the actual code to resolve other issues, particularly with some special characters that are expected to be encoded.

Here are a few examples of CDATA implementation in HTML tags:

<script type="text/javascript">
/* <![CDATA[ */
...
/* ]]> */
</script>

<script type="text/javascript">// <![CDATA[
...
// ]]>
</script>

<style type="text/css">
/* <![CDATA[ */
...
/* ]]> */
</style>