« XUL Reference
currentIndex
Type: integer
Set to the index of the currently focused item in the list. If no item is focused, the value will be -1. (or, on some platforms, typeof(listboxcurrentIndex) will be undefined) In a single selection list, the current index will always be the same as the selected index. In a multiple selection list, the currently focused row may be modified by the user without changing the selection by pressing the Control key and pressing the cursor keys to navigate.