Tab selection order is determined by the value of tabIndex as follows:
All elements with tabIndex > 0 are selected in increasing tab index order, or in source order for duplicate tab index values.
All elements with tabIndex = 0, or without tabIndex set, are selected next, in source order if more than one.
Elements with tabIndex = -1 are omitted from tabbing order.
This property has read-write permissions, meaning you can change as well as retrieve its current value.