Poor man's AJAX: Browser-side XSLT transformation in IFRAME

One of the oldest methods to provide AJAX-like functionality in a browser that does not support XmlHttpRequest object is loading the dynamic content into a hidden IFRAME. It’s an unreliable technique that should not be used, but it can still provide a viable workaround in scenarios where you need to perform browser-side XSLT transformation in browsers with lousy JavaScript-based XSLT support (it looks like Chrome is still in this category).

This is a conceptual step-by-step description of the process:

  • Create a hidden IFRAME in the main page.
  • Define a callback function in the main page that will receive the results of the transformation. This callback function will have to insert the transformation results into the main page’s HTML/DOM structure.
  • When you need to download additional content, set the IFRAME.href attribute to the URL of the dynamic content.

You should use a timeout in the main page to capture failed loads of the dynamic content. The timeout code should display an error message and kill the download process in IFRAME by resetting the IFRAME.href attribute.

  • The dynamic content loaded into the IFRAME should have XML MIME type and contain the xml-stylesheet processing instruction. This will cause the browser to perform XSLT transformation on the XML data.
  • The resulting HTML should include JavaScript call of the callback function in the parent frame, for example <body onload="parent.callback(document.body.innerHTML)">

Alternatively, you can use the onload handler in the IFRAME element to call the callback function.

Firefox forgets to create document.body object on Linux

If you use client-side XSLT transformations driven by xml-stylesheet pseudo-instruction in XML documents, you might encounter interesting problems when using Firefox 2 on Linux. When the  HTML page is created with XSLT transformation, Firefox does not create the document.body object, causing JavaScript libraries (for example, jQuery) to break.

Workaround: add an ID to your body tag (for example, <body id="body">) and fix the document.body object after the DOM is ready. To do it in jQuery, use the following code:

$(function() {   if (!document.body) document.body = $('#body').get(0); }

XSLT transformation in ASP: non-standard XML encoding

If you want to generate documents with non-standard encodings with server-side XSLT transformation in IIS/ASP environment, you should:

  • Set the Response.Charset property to the desired character set;
  • Set the Response.Codepage property to the desired code page (or use the <%@ LANGUAGE="VBScript" CODEPAGE="codepage" %> directive in your ASP script).
  • Omit XML declaration from the translated text (using omit-xml-declaration=”yes” attribute in xsl:output element) and prepend the desired XML declaration in front of the translated text.

For example, the following program generates XML (or XHTML) document encoded in windows-1250 character set (codepage: 1250) …

Const DOMClass = "MSXML2.DOMDocument"
Set XSLT = Server.CreateObject(DOMClass)
Set XDoc = Server.CreateObject(DOMClass)
XDoc.loadXML("<root greek='&#946;' ee='č' />")
Response.Charset = "windows-1250"
Response.Codepage = 1250
Response.ContentType = "text/xml"
Response.Write "<?xml version='1.0' encoding='windows-1250'?>"
Response.Write XDoc.transformNode(XSLT)

… when using the following XSL transformation:

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" omit-xml-declaration="yes" />
… rest deleted …