RegExp For Date

i have this function to check date (not mine)

function (s_date) {
// check format
if (!re_dt.test(s_date))
return false;
// check allowed ranges
if (RegExp.$1 > 31 || RegExp.$2 > 12)
return false;
// check number of day in month
var dt_test = new Date(RegExp.$3, Number(RegExp.$2-1), RegExp.$1);
if (dt_test.getMonth() != Number(RegExp.$2-1))
return false;
return true;}

it will check in this format DD-MM-YYYY
is it possible to modify it to be (MM/DD/YYYY OR DD/MM/YYYY) in one function?