Saxon » SaxonJS

I am trying to understand how xsl:result-documents can be handled with Node and Saxon-JS 2 and the async use of the transform function. The documentation at http://saxonica.com/saxon-js/documentation/index.html#!api/transform is rather long but in the section about deliverResultDocument it says:

If the save property is absent, the default implementation saves the value in options.resultDocuments[URI], for return to the calling application.

Is that meant to say that the option passed into transform receives these result documents in a resultDocuments object? Or is the result the Promise returns supposed to have a resultDocuments property by default?

I suppose the latter is meant.

However, when trying to rely on that default, I get an error:

PS C:\Users\marti\SomeDir> node .\return-xml-test1.js
Transformation failure: TypeError: N.save is not a function
TypeError: N.save is not a function
    at e (C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:778:362)
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:782:192
    at b (C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:357:642)
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:357:865
    at Array.forEach (<anonymous>)
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:357:838
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:357:865
    at Array.forEach (<anonymous>)
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:357:838
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:388:385
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:401:122
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:357:865
    at Array.forEach (<anonymous>)
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:357:838
    at Object.push (C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:406:435)
    at c (C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:5423:371)
    at C:\Users\marti\node_modules\saxon-js\SaxonJS2N.js:5463:480

The Javascript code is

require('saxon-js');

SaxonJS.transform(
    {
        'stylesheetFileName': 'return-xml-test1.sef',
        'destination': 'document',
        'resultForm': 'default',
        'deliverResultDocument': uri => {
            return { 'destination': 'document' }
        }
    },
    'async'
    )
    .then(result => console.log(result))
    .catch(error => console.log(error)
);

the stylesheet as XSLT is

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    version="3.0"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:array="http://www.w3.org/2005/xpath-functions/array"
    xmlns:ixsl="http://saxonica.com/ns/interactiveXSLT"
    expand-text="yes"
    exclude-result-prefixes="#all">

  <xsl:output method="xml" indent="yes"/>

  <xsl:template name="xsl:initial-template">
    <root>prinicipal result</root>
    <xsl:iterate select="1 to 5">
        <xsl:call-template name="output-xml">
          <xsl:with-param name="value" select="."/>
        </xsl:call-template>
    </xsl:iterate>
  </xsl:template>

  <xsl:template name="output-xml">
    <xsl:param name="value"/>
    <xsl:result-document href="xml-result-{$value}.xml" method="xml">
      <result name="result-{$value}">Result {$value}</result>
    </xsl:result-document>
  </xsl:template>

</xsl:stylesheet>

Have I misunderstood that sentence about "If the save property is absent, the default implementation saves the value in options.resultDocuments[URI]"?