>IE 11 has virtually NO support for ES6 - see https://kangax.github.io/compat-table/es6/ (and MS support has ended so it probably never will). Edge, OTOH, has if pretty much fully ES6 compliant.
>
>Personally I don't even try to support IE - but they are not 'public' sites and we can specify/recommend which browsers can/should be used. If you really have to support IE11 then probably best stick to ES5 (with Typescript) ?

Thanks, Viv. I may discuss it today at our meeting if we would have time (we used to have just that project meetings, but now it was consolidated into every company's developer meeting so there is less chance to discuss technical issues in a group :(). I would not know we had issues if my colleague would not use IE for his development and tests.