Do you mean you want to use the result in JavaScript?
Then just use XSL to compute the count within some hidden
HTML form, then Javascript will have access to it when the
page is loaded in the browser, via the form object tree. Note
though that this approach is browser specific.
..thats overly complicated isn't it? Why not just fill in the values:
<xsl:template match="/">
<html>
<head>
<script>
var count = <xsl:value-of select="count(//whatever)"/>;<xsl:text/>
</script>
</head>
</html>
</xsl:template>
Gives:
<script>
var count = n;
</script>
cheers
andrew