A text input area with a popup, which typically presents a dropdown list of
choices, but could just as easily provide choices in other ways. The user can always
choose to enter their own arbitrary text as well; they are not limited to the indicated
choices. See ListComboBox
for typical subclasses.
The HTML5 specification calls for a
datagrid element which can be used to
create combo boxes, but that only supports a rather narrow definition of what a combo
box can do. Even once datagrid
is broadly supported, the ComboBox class still has a role to play as a
base class for custom combo boxes.