Elements order in a “for (… in …)” loop

Question

Does the \"for…in\" loop in Javascript loop through the hashtables/elements in the order they are declared? Is there a browser which doesn\'t do it in order?
The object

Answer 1

The elements of an object that for/in enumerates are the properties that don't have the DontEnum flag set. The ECMAScript, aka Javascript, standard explicitly says that "An Object is an unordered collection of properties" (see http://www.mozilla.org/js/language/E262-3.pdf section 8.6).

It's not going to be standards conformant (i.e. safe) to assume all Javascript implementations will enumerate in declaration order.