Definition
HTML Standard defines HTMLAllCollection
[Exposed=Window,
LegacyUnenumerableNamedProperties]
interface HTMLAllCollection {
readonly attribute unsigned long length;
getter Element (unsigned long index);
getter (HTMLCollection or Element)? namedItem(DOMString name);
(HTMLCollection or Element)? item(optional DOMString nameOrIndex);
// Note: HTMLAllCollection objects have a custom [[Call]] internal method and an [[IsHTMLDDA]] internal slot.
};