Javascript Containers Map, Set - supported?

[StevenFS]

Are Javascript containers like Map, Set and member functions like Set.has() supported by QML Javascript? I'm getting errors like this:

qrc:/CheckTypes.js:9: ReferenceError: Set is not defined
qrc:/CheckTypes.js:31: TypeError: Cannot call method 'has' of undefined

"the QML runtime implements the ECMAScript Language Specification standard."
http://doc.qt.io/qt-5/qtqml-javascript-hostenvironment.html

// CheckShapes.js
.pragma library

var shapes = new Set(["Circle", "Triangle", "Square"]);

function isShape(polygon) {
	return shapes.has(polygon);
}

// my.qml
import QtQuick 2.9
import "qrc:/CheckShapes.js" as Foo

RowLayout {
  id: bar
  visible: (Foo.isShape(myPolygon.name));  // Errors 
};

RowLayout {
  id: bar2  // This one works.
  visible: (myPolygon.name === "Circle"   || 
            myPolygon.name === "Triangle" || 
            myPolygon.name === "Square");
}

My understanding is that QML fully supports the inclusion of JavaScript files. I've written a lengthy .js file to be imported and used within .qml files. My Javascript's rusty but syntax is mostly copy+pasted from Mozilla.org documentation.

Am I missing a declaration at the top of my .js file to import standard JavaScript types? A compiler flag in my QTCreator Kit? Syntax error?

--
Environment:
Apple MacOS: 10.13.3
QT Creator: 4.5.1 Based on 5.10.1 (Feb 10 2018, rev. 24cd0b1cd6)
Project: QT 5.9.2

[jpnurmi]

Unfortumately, the QML engine does not support ECMAScript 2015 aka ES6.

The QML runtime implements the 5th edition of the standard

https://bugreports.qt.io/browse/QTBUG-47735

[StevenFS]

Unfortumately, the QML engine does not support ECMAScript 2015 aka ES6.
@jpnurmi

Thank you @jpnurmi. Knowing JavaScript Frameworks exploded in popularity in the early 2000's I had no idea standard containers weren't added till 2015 nor that QML lagged that far behind the standard. Re-writing with arrays, my code fully doubled in size and went from near Constant Time to Linear. Disappointing. I guess that's just how it is.

[6thC]

Well, there is some it seems... just not all? I note there's quite a few comments: // ECMAScript 6 @: http://doc.qt.io/qt-5/qtqml-javascript-functionlist.html

While I've not used it - that page has:
map(callbackfn [, thisArg])
but not Set.. not sure if that helps...