BS4 DropDown onclick fires 3 times

I was trying to capture the final result of the changing of a BS4 DropDown. The onclick event was where I started. I noticed that the user does click the control twice: once to activate the dropdown and a second time to select their item. Not sure why the third onclick event occurs.

Is there another event that I can use that would be equivalent to onchange (which doesn’t appear to exist for DropDowns) that only fires once after the user has completed their selection?

Are you checking the type of event?

Dropdown1.onclick = function(s) {
    if (typeof(s) == "object") {
    NSB.MsgBox(s + " " + Dropdown1.selection);