Saxon » SaxonJS

When I run

require('saxon-js');

var result = SaxonJS.XPath.evaluate(`
  fold-left(
    (map { 'a' : 1, 'b' : 2}, map { 'a' : 3, 'b' : 4 }, map { 'a' : 1, 'b' : 2} ),
    (), 
    function($distinct-maps, $new-map) {
      if (some $map in $distinct-maps satisfies deep-equal($map, $new-map))
      then $distinct-maps
      else ($distinct-maps, $new-map)
    }
  )
`);

console.log(result);

with Saxon-JS 2 and node on Windows I get the error

C:\Users\marti\SomeDir\node_modules\saxon-js\SaxonJS2N.js:218
{};b.currentTemplate=null;b.focus=null;b.localVars=this.closureContext.localVars.slice();b.currentComponent=this.closureContext.currentComponent;c=this.declaredArgs;for(var d=0;d<a.length;d++){var f=parseInt(c[d].slot,10);b.localVars[f]=a[d]}return Expr$$module$temp$js$source$src$Expr.evaluate(this.body,b)};var f=function(b,c,d){b=a.call(this,b,b.alphaTree.a.length)||this;b.baseFunction=c;b.fixedValues=d;return b};$jscomp.inherits(f,a);f.prototype.identify=function(){return"partially-applied "+this.baseFunction.identify()};
                                                                                 ^

TypeError: this.closureContext.localVars.slice is not a function
    at n.evaluate (C:\Users\marti\SomeDir\node_modules\saxon-js\SaxonJS2N.js:218:82)
    at u.evaluate (C:\Users\SomeDir\node_modules\saxon-js\SaxonJS2N.js:220:66)
    at C:\Users\marti\SomeDir\node_modules\saxon-js\SaxonJS2N.js:547:123
    at Array.forEach (<anonymous>)
    ...

In the browser I get a similar error

Uncaught TypeError: this.fl.Ha.slice is not a function
    at d.evaluate (SaxonJS2.rt.js:283)
    at a.evaluate (SaxonJS2.rt.js:284)
    at SaxonJS2.rt.js:508
    at Array.forEach (<anonymous>)
    at t (SaxonJS2.rt.js:508)
    at fold-left (SaxonJS2.rt.js:525)
    at SaxonJS2.rt.js:632
    at Object.a [as evaluate] (SaxonJS2.rt.js:591)
    at Object.evaluate (SaxonJS2.rt.js:789)
    at <anonymous>:1:15