When code is paused and you hover a key of an object, this will refer to things that they are not...
<div id="test"></div>
debugger;
var z = "z";
var x = {
test: 1,
x: 1,
y: 1,
z: 1
};Will refer the div when you hover "test",
Shows "undefined" for x and z.
Shows nothing for y.
IMO it should not display anything for any key.