Why Split `` Tags Using `document.write()`?

Document.write() Script Tag Splitting: A Rationale

In web development, it's not uncommon to encounter scripts written using document.write() that split the <script> or /script> tags. This practice may raise the question, "Why employ such a technique?"</p> <p><strong>Reason for Splitting:</strong></p> <p>The answer lies in the way HTML parsers handle CDATA sections within <script> elements. While SGML dictates that a <script> block should terminate upon encountering any end-tag open sequence (e.g., </), browsers only recognize an actual </script> close-tag as the end of a script block.

Significance of Splitting:

Consider the following example:

<script type='text/javascript'>
  document.write('<scr' + 'ipt type="text/javascript" src="script.js"></sc' + 'ript>');
</script>

In this case, if the <script> tag were not split, the close-tag sequence </sc would be interpreted as the end of the enclosing <script> block, prematurely terminating the script. Splitting the tag ensures that the browser correctly parses and executes the entire script.</p> <p><strong>XHTML and Script Writing:</strong></p> <p>In XHTML, there is no special handling for script blocks. Characters such as < and & must be escaped within scripts. However, using unescaped characters can lead to confusion in browsers parsing XHTML as HTML.</p><p><strong>Alternative Script Writing:</strong></p><p>To cater to both XHTML and HTML parsers, consider using the following approach:</p><pre class="brush:php;toolbar:false"><script type="text/javascript"> document.write('\x3Cscript type="text/javascript" src="script.js"></script>');

By escaping the characters using hexadecimal notation, you ensure that the script will be correctly interpreted by all parsers.

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