Hi Martin,
   Thanks for the answer.

Deriving from your XSLT stylesheet, I wrote following that works,

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"

                         xmlns="http://www.w3.org/2005/xpath-functions"

                         version="3.0">

    <xsl:output method="text"/>

    <xsl:template match="root">
        <map>
            <map key="{local-name()}">
                <array key="val">
                    <xsl:apply-templates/>
                </array>
            </map>
        </map>
    </xsl:template>

    <xsl:template match="val">
        <!--<number>{.}</number>-->
        <number><xsl:value-of select="."/></number>
    </xsl:template>

    <xsl:template match="/">
        <xsl:variable name="json-xml">
            <xsl:apply-templates/>
        </xsl:variable>
        <xsl:value-of select="xml-to-json($json-xml, map { 'indent' :
true() })"/>
    </xsl:template>

</xsl:stylesheet>

If I write, <number>{.}</number> in above stylesheet, as you've suggested
instead of mine <number><xsl:value-of select="."/></number>, I get
following error

xml-to-json: Invalid number: {.}
(produced by Saxon PE)

Any idea, why this is so?

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
> <http://www.w3.org/1999/XSL/Transform>
>
>     xmlns:xs="http://www.w3.org/2001/XMLSchema"
> <http://www.w3.org/2001/XMLSchema>
>     exclude-result-prefixes="#all"
>     xmlns="http://www.w3.org/2005/xpath-functions"
> <http://www.w3.org/2005/xpath-functions>
>     expand-text="yes"
>     version="3.0">
>
>   <xsl:mode on-no-match="shallow-skip"/>
>
>   <xsl:output method="text"/>
>   <xsl:strip-space elements="*"/>
>
>   <xsl:template match="root">
>       <map>
>           <map key="{local-name()}">
>               <array key="val">
>                   <xsl:apply-templates/>
>               </array>
>           </map>
>       </map>
>   </xsl:template>
>
>   <xsl:template match="val">
>       <number>{.}</number>
>   </xsl:template>
>
>   <xsl:template match="/">
>      <xsl:variable name="json-xml">
>          <xsl:apply-templates/>
>      </xsl:variable>
>      <xsl:value-of select="xml-to-json($json-xml, map { 'indent' : true()
> })"/>
>   </xsl:template>
>
> </xsl:stylesheet>
>




-- 
Regards,
Mukul Gandhi