Active/open class on collection

[GillesVermeulen]

It would be useful if an extra class was added to a collection button if it was opened. This way open collection buttons can be styled differently.

[DataTables]

Good point - I like that idea.

[AllanJard]

There is the aria-expanded attribute which is either true or false. That could be used as a selector to determine whether styles should be added or not.