XSLT Logic, Loops & Sorting (for-each, if, choose)

In Plain English

XSLT provides rich procedural and functional flow constructs: <xsl:for-each> iterates over node sets, <xsl:sort> sorts elements before rendering, <xsl:if> provides conditional checks, and <xsl:choose>/<xsl:when>/<xsl:otherwise> enables multi-way switch branching.

The Mental Model

"XSLT logic tags are like a spreadsheet pivot table: you can loop through every row (<xsl:for-each>), sort alphabetically (<xsl:sort>), highlight VIP accounts in red (<xsl:if>), and assign category badges (<xsl:choose>)."

Deep Dive: How It Works

<xsl:for-each select="path">: Loops through all matching elements.

<xsl:sort select="field" order="ascending|descending" />: Sorts nodes inside for-each.

<xsl:if test="boolean_xpath">: Renders content only if condition evaluates to true.

<xsl:choose>: Multi-branch container with <xsl:when test="..."> and <xsl:otherwise> fallback.

Syntax Blueprint

<xsl:for-each select="catalog/book">
  <xsl:sort select="price" />
  <xsl:if test="price &gt; 30">...</xsl:if>
</xsl:for-each>

Loops over books, sorts by price, and conditionally formats expensive titles.

Core Rules to Remember

<xsl:for-each>: Iterates repeating collection nodes without manual counter variables.

<xsl:sort>: Sorts output by text or numeric data values.

<xsl:choose>: Clean if/else-if/else branching mechanism in XSLT stylesheets.

Common Beginner Traps & How to Fix Them

Mistake:Using raw > or < in xsl:if test expressions.

Why it happens: XSLT is valid XML, so unescaped > breaks XML parser syntax.

How to fix: Always write > for > and < for < inside test attributes (e.g. test="price > 50").

Pro Tip: Place <xsl:sort> as the first child immediately inside <xsl:for-each> to ensure proper sort order execution.

Live Interactive Example

Hit Run Code to see it live

Full XSLT Loop, Sort and Conditional Table

XML 1.0 / XSD

Live Browser Preview

Click "Preview / Apply" to view the rendered output.

How it works: Sorts books descending by price and classifies them with xsl:choose.

Your Turn: Micro Challenge

No pressure! Edit the starter code below and test your solution with instant feedback.

Micro Exercise

Filter items with xsl:if

Write an `<xsl:if test="stock > 0">` that outputs `<p>In Stock</p>` inside.

Sandbox Output

Click "Run & Check" to test your solution.

Finished reading and practicing?

Mark this lesson as completed to update your course progress.

Deep Dive: How It Works

<xsl:for-each select="path">: Loops through all matching elements.

<xsl:sort select="field" order="ascending|descending" />: Sorts nodes inside for-each.

<xsl:if test="boolean_xpath">: Renders content only if condition evaluates to true.

<xsl:choose>: Multi-branch container with <xsl:when test="..."> and <xsl:otherwise> fallback.