When and Why Should We Use CDATA Sections in Script Tags?

CDATA Sections in Script Tags: When and Why They Matter

CDATA (character data) sections provide a way to embed non-parsed data within an XML or HTML document. In the context of script tags, CDATA sections can be used to prevent the browser from interpreting certain characters within the code as markup.

When to Use CDATA Sections

It is generally preferable to use CDATA sections for inline JavaScript in XHTML documents that are intended to be parsed as XML. This is because XHTML treats inline JavaScript as parsed character data by default, which can lead to issues when the code contains characters that are also used in XML markup.

For example, the following code will not parse correctly as XHTML:

<script type="text/javascript">
//<![CDATA[
>>> i<10
//]]>
</script>

This is because the string "i<10" contains the '<' character, which is used to start XML tags. The browser will attempt to interpret this as a tag, causing the script to fail.

How to Use CDATA Sections

To prevent this issue, you can wrap the JavaScript code in a CDATA section, as follows:

<script type="text/javascript">
//<![CDATA[
>>> i<10
//]]>
</script>

The CDATA section will tell the browser to ignore everything between the '' markers as markup, allowing the JavaScript code to run correctly.

Note on External Scripts

It is important to note that CDATA sections are not necessary for JavaScript code that is stored in external source files. This is because the browser will always treat external scripts as character data, regardless of the markup surrounding them.

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