Tutorial generates error in `class HelloGNOME`
I'm following this introductory tutorial: https://developer.gnome.org/gnome-devel-demos/unstable/hellognome.js.html.en and it's generating this error:
(gjs:15411): Gjs-CRITICAL **: JS ERROR: SyntaxError: class is a reserved identifier @ ./welcomegnome.js:10
On this line:
class HelloGNOME {
Ubuntu 16.04.6 LTS, Unity Desktop, freshly installed gjs
today, Kernel 4.14.134 and JRE 8
I've spent time googling this error but have come up empty handed. Any clues?