if element value is a number : number function « XSLT stylesheet « XML Tutorial

1. XML Tutorial
2. XSLT stylesheet
3. number function

File: Data.xml
<?xml version="1.0" encoding="utf-8"?>
<data>

    <number>253</number>
    <number>sd12</number>
    <number>-64</number>
    <number>2.25.25</number>
    <number>2.25</number>
</data>
File: Transform.xslt

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
      version="1.0"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="number">
      <DIV>
        <xsl:value-of select="."/>
        <xsl:if test="string(number(.))='NaN'"> is not a number</xsl:if>
      </DIV>
    </xsl:template>
</xsl:stylesheet>
Output:

<?xml version="1.0" encoding="UTF-8"?>

    <DIV>253</DIV>
    <DIV>sd12 is not a number</DIV>
    <DIV>-64</DIV>
    <DIV>2.25.25 is not a number</DIV>
    <DIV>2.25</DIV>