How to check if an object is an instance of a NodeList in IE?

Question

Why is NodeList undefined in IE6/7?

Answer 1

Adam Franco's answer almost works. Unfortunately, typeof el.item returns different things in different version of IE (7: string, 8: object, 9: function). So I am using his code, but I changed the line to typeof el.item !== "undefined" and changed == to === throughout.

if (typeof el.length === 'number' 
    && typeof el.item !== 'undefined'
    && typeof el.nextNode === 'function'
    && typeof el.reset === 'function')
{
    alert("I'm a NodeList");
}