mark_ablov

var names = Object.getOwnPropertyNames(obj);
for (var i = 0, len = names.length; i < len; ++i)
{
    obj['prop' + i] = i;
    names = Object.getOwnPropertyNames(obj);
    len = names.length;
}

var date = new Date('08/31/2011');
var N = 1;
date.setMonth(date.getMonth() + N);
date.setDate(0);
alert(date);