Scripted extensions are very similar to Java extensions, except the extension is implemented inside of the xalan:script element:

<xsl:stylesheet version="1.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xalan="http://xml.apache.org/xslt"
xmlns:MyExt="xalan://com.AcmeX.MyExtensionElement">
extension-element-prefixes="MyExt">
  
<xalan:component prefix="rep" elements="repeat">
  <xalan:script lang="javascript">
    function superExtension(ctx, elem)
    {
      /* ... */
      return null ;
    }
  </xalan:script>
</xalan:component>
   
<xsl:template match="*">
     <myExt:superExtension attr1="val1" attr2="val2">
        <!-- ... -->
     <myExt:superExtension>
</xsl:template>
</xsl:stylesheet>

As with Java, the return value is placed into the result tree, but you return null to disable this effect with scripting languages. See Recipe 12.13 for an example.