var el = document.createElement("a");
Chrome dev channel (6.0.472.0 (Official Build 53024) dev, WebKit 534.3) outputs "undefined". Firefox and Opera output "string". Discussion in #whatwg concluded that the relevant spec here is WebIDL:
But no one who was awake was able to decipher what it actually required here. WebKit seems like the one that's wrong here, but I'm not totally sure on that.
Maciej Stachowiak reports that the test gives "string" in Safari, so it's presumably a bug in the V8 bindings.
Hey Nate, looks like a bindings generation bug.
This bug is a consequence of the way V8 bindings are generated. V8 generates IDL attributes as properties on the object. The Web IDL spec specifies them as getters and setters on the object's prototype . If bug 49739 was fixed, this bug would also be fixed as a natural consequence.