See also !526 (closed)
This does port our code from jquery to vanilla DOM. However, we still depend on jquery because it is a dependency for bootstrap 4 as well as bootstrap-datepicker. So this is only a first step.
Jquery's event handeling is one of the few areas for which there are still no equivalent functions in vanilla DOM, so I created some helpers under the
I used some more recent JS/DOM features:
All of these are supported in modern browsers, but not in IE, which is basically EOL at this point. (bootstrap 5 will also drop support for IE).