Date validation in javacript

validate date format e.g. 12-2-2004,12-11-08 function validateDate() { obj=//name of your object msg=//your mesage comes here var validNum = /^([0-9]{1,2})-([0-9]{1,2})-([0-9]{2,4})$/; if (validNum.test(obj.value) == false) { alert(msg); obj.focus(); //obj.select(); return false; } return true; }