Use of class fields
We currently use es6 public class fields in many places, like this example
https://gitlab.com/internet4000/radio4000-cms/-/blob/master/js/radio4000/radio4000-nav-main.js#L5
Unfortunately it doesn't work in IE, iOS, Safari and Firefox for Android yet:
https://caniuse.com/#feat=mdn-javascript_classes_public_class_fields
I think the support is so bad that we can't use this otherwise super nice feature..