Recently, I was trying to pass some info from my Javascript into my XSL stylesheet. Here’s how I finally did it:

(Quick note: in real life, I don’t name variables "myThis" and "myThat"; I’m just doing it here to make it clear what is my code and what is part of XSL, AJAXSLT, Javascript, etc.)

The XSL

<xsl:stylesheet version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:param name="myParam" select="'myDefault'"/>
  <xsl:template match="/">
    myParam: <xsl:value-of select="$myParam"/>
  </xsl:template>
</xsl:stylesheet>

The Javascript

var myContext = new ExprContext(myXml);
myContext.setVariable("myParam",
    new StringValue("the value for myParam"));
xsltProcessContext(myContext, myXsl, myRootElement);

The Trick

So the big trick, which I figured out after reading lots of the AJAXSLT code, was to set the parameter to a StringValue, rather than a regular Javascript String. StringValue is part of AJAXSLT. Update: Will, in the comments below, mentions that there are four total types: StringValue, NumberValue, BooleanValue and NodeSetValue.

Troubleshooting

Don’t forget to declare your parameter with <xsl:param.../> before using it with <xsl:value-of select="$..."/>, otherwise Ajaxslt will blow up in the middle of rendering.

It took a bit of playing to get it to work. Here’s some sample code. (I forgot to write it up when I did it, so I might have left something out.)

Setup

First, include the scripts. Note: make sure to have a closing </script> tag rather than doing <script ... /> because that silently fails on some browsers (yay!).

<!-- AJAXSLT -->
<script src="/ajaxslt/misc.js"
    type="text/javascript"></script>

<script src="/ajaxslt/dom.js"
    type="text/javascript"></script>

<script src="/ajaxslt/xpath.js"
    type="text/javascript"></script>

<script src="/ajaxslt/xslt.js"
    type="text/javascript"></script>

<script src="/ajaxslt/xpathdebug.js"
    type="text/javascript"></script>

Using Ajaxslt for XSL Transformation

For XSL transformation, you’ll need three things: some XML, some XSL, and a node (or DocumentFragment presumably) to place the result in. One way to get the XML and XSL is to load them through an XmlHttpRequest. Ajaxslt also provides a couple of handy functions to convert between text and XML:

var myText = "...";
var myXml = xmlParse(myText);
var myTextAgain = xmlText(myXml);

Once you’ve got the XML and XSL, you’re ready to do the transformation:

var myNode = document.getElementById("myId");
xsltProcessContext(new ExprContext(myXml), myXsl, myNode);

Your node should now contain the result of the transformation.

Using Ajaxslt for XPath

You can also use Ajaxslt for XPath evaluation, which is really handy when writing tests on your rendered document:

var expr = xpathParse(myXpathString);
var result = expr.evaluate(new ExprContext(myXmlDocument));
var resultAsString = result.stringValue();

Troublshooting

The order of the JavaScript include statements matters: if Ajaxslt is giving strange errors, make sure the scripts are included in the exact same order as in the Setup section of this page.

Make sure you know what you’re passing to Ajaxslt: if you’re sending request.responseXML to a method, don’t look at request.responseText to see what you’re passing; use xmlText(request.responseXML).

The root element isn’t selectable: if your XML is <foo id="myId">...</foo>, then you don’t select foo’s id with /foo/@id but rather with just @id.

Case matters in xpath: If you’re evaluating an xpath expression on an HTML DOM, note that the node names are most likely uppercase. So do /HTML/BODY instead of /html/body