Definition
HTML Standard defines HTMLOptionsCollection
[Exposed=Window]
interface HTMLOptionsCollection : HTMLCollection {
// inherits item(), namedItem()
[CEReactions] attribute unsigned long length; // shadows inherited length
[CEReactions] setter undefined (unsigned long index, HTMLOptionElement? option);
[CEReactions] undefined add((HTMLOptionElement or HTMLOptGroupElement) element, optional (HTMLElement or long)? before = null);
[CEReactions] undefined remove(long index);
attribute long selectedIndex;
};