[Interest] ECMA-262 Spec?

[Jason H]

According to http://doc.qt.io/qt-5/qtqml-javascript-hostenvironment.html, Qt supports 5th ed. But accordign to https://en.wikipedia.org/wiki/ECMAScript#Implementations, Qt supports 6th ed.  I give equal odds to Qt docs being out of date as much to the Wiki being wrong.

What's the status of being able to use 6th ed features (classes, 'of', etc)? I heard about some updates to V4, but https://wiki.qt.io/index.php?title=V4 is light on details.