Both document.getElementsByTagName('div') and document.querySelectorAll('div') return NodeList collection. The only difference is that first method returns live-collection and second one - a static one.
The question is - is there any opportunity to distinguish one object from another only via inspecting these objects (i.e - not trying to add/remove some items to test "liveness")?
The NodeList interface is agnostic of its dead or live status.
interface NodeList {
Node item(in unsigned long index);
readonly attribute unsigned long length;
};
It only contains a property length, and a method item so I'm afraid it's currently not possible to determine if an object is live without manipulating the DOM and seeing the effects.