function test() { var values = [undefined, null, Math, objectEmulatingUndefined()]; var expected = [true, true, false, true]; for (var i=0; i<100; i++) { var idx = i % values.length; if (values[idx] == undefined) assertEq(expected[idx], true); else assertEq(expected[idx], false); if (null != values[idx]) assertEq(expected[idx], false); else assertEq(expected[idx], true); } } test();