xslt-lab/site/content/xslt/functions/xsl-array-member.md

title, description, date, version, versionLabel, category, syntax, tags

title	description	date	version	versionLabel	category	syntax	tags
xsl:array-member	Defines a single member inside an xsl:array; the member value is any XDM sequence, including nested arrays, maps, or empty sequences.	2026-04-18T00:00:00Z	3.0	XSLT 3.0	element	<xsl:array-member select="expression"/>	xslt reference xslt3

Description

xsl:array-member contributes one positional slot to the enclosing xsl:array. The value of the member is provided either through the select attribute (an XPath expression) or through a sequence constructor in the element content.

The key distinction of xsl:array-member is that its value is a sequence — not necessarily a single item. A member can be the empty sequence (), a single integer, a sequence of strings, or even a nested map or array. This capability is what makes XDM arrays different from flat XPath sequences: arrays can contain heterogeneous multi-value slots.

When using select, the expression is evaluated and the resulting sequence becomes the member. When using content, the sequence constructor result becomes the member. You cannot use both select and content simultaneously.

In loops (xsl:for-each), each iteration of the loop body that contains an xsl:array-member adds one member to the enclosing array. This lets you build arrays of arbitrary length from input data.

Attributes

Attribute	Type	Required	Description
select	expression	No	XPath expression whose result becomes the member value. Mutually exclusive with content.

Examples

Building a JSON array with mixed types

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<metrics>
  <metric name="response_time" value="142"/>
  <metric name="error_rate" value="0.03"/>
  <metric name="uptime" value="99.9"/>
</metrics>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xsl:output method="json" indent="yes"/>

  <xsl:template match="/metrics">
    <xsl:array>
      <xsl:for-each select="metric">
        <xsl:array-member>
          <xsl:map>
            <xsl:map-entry key="'name'" select="string(@name)"/>
            <xsl:map-entry key="'value'" select="xs:double(@value)"/>
          </xsl:map>
        </xsl:array-member>
      </xsl:for-each>
    </xsl:array>
  </xsl:template>
</xsl:stylesheet>

Output (JSON):

[
  {"name": "response_time", "value": 142},
  {"name": "error_rate", "value": 0.03},
  {"name": "uptime", "value": 99.9}
]

Array of sequences demonstrating multi-value members

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:array="http://www.w3.org/2005/xpath-functions/array">
  <xsl:output method="xml" indent="yes"/>

  <!-- Each group of tags stored as a sequence in one array slot -->
  <xsl:template match="/articles">
    <xsl:variable name="tag-groups">
      <xsl:array>
        <xsl:for-each select="article">
          <xsl:array-member select="tag/string()"/>
        </xsl:for-each>
      </xsl:array>
    </xsl:variable>
    <result>
      <!-- Tags for first article -->
      <article-1-tags>
        <xsl:value-of select="array:get($tag-groups, 1)" separator=", "/>
      </article-1-tags>
    </result>
  </xsl:template>
</xsl:stylesheet>

Notes

• xsl:array-member must appear inside xsl:array (directly or via instructions that produce array members).
• An xsl:array-member with an empty sequence value creates a slot containing (), which is distinct from the slot not existing.
• Using select="()" explicitly creates an empty-sequence member, valid in XDM.
• In JSON output mode, an array member that is the empty sequence is serialised as null.

See also

• xsl:array
• array:get()