Order of iterating Javascript object properties?

Question

If I have this code :

o["a"]=1;
o["b"]=1;
o["c"]=1;
o["d"]=1;


for (var k in o)
{
  alert(k)
}

• Would it always(cross browser) be alerted in the same order as the attribute were added ?

• And what about this ? (same question)

  var o={a:1,b:1,c:1,d:1} ?

Answer 1

No. The order is not specified. From the spec:

The mechanics and order of enumerating the properties ... is not specified.