xslt check if string is null or empty

Question

how chan i check if a value is null or empty with xsl?

eg if categoryName is empty? im using a when choose construct

eg:

 <xsl:choose>
    <xsl:when test="categoryName !=null">
        <xsl:value-of select="categoryName " />
      </xsl:when>
      <xsl:otherwise>
        <xsl:value-of select="other" />
      </xsl:otherwise>
 </xsl:choose>

Answer 1

test="categoryName != ''"

Answer 2

From here:

to test if the value of a certain node is empty

Depends what you mean by empty.

• Contains no child nodes: not(node())
• Contains no text content: not(string(.))
• Contains no text other than whitespace: not(normalize-space(.))
• Contains nothing except comments: not(node()[not(self::comment())])

Answer 3

Absent of any other information, I'll assume the following XML:

<group>
    <item>
        <id>item 1</id>
        <CategoryName>blue</CategoryName>
    </item>
    <item>
        <id>item 2</id>
        <CategoryName></CategoryName>
    </item>
    <item>
        <id>item 3</id>
    </item>
    ...
</group>

A sample use case would look like:

<xsl:for-each select="/group/item">
    <xsl:if test="CategoryName">
        <!-- will be instantiated for item #1 and item #2 -->
    </xsl:if>
    <xsl:if test="not(CategoryName)">
        <!-- will be instantiated for item #3 -->
    </xsl:if>
    <xsl:if test="CategoryName != ''">
        <!-- will be instantiated for item #1 -->
    </xsl:if>
    <xsl:if test="CategoryName = ''">
        <!-- will be instantiated for item #2 -->
    </xsl:if>
</xsl:for-each>