text box length validation

[woodplease]

hi. i want to be able to check that a users inputted card number is 16 digits in length, but i cant seem to be able to do it.

Just a simple javascript function is all i really need

 

Any help would be great, thanks.

[KevinM1]

function checkCreditCard(cardNum) {
   var regEx = /^\d{16}$/;

   if (!cardNum.match(regEx)) {
      alert("Credit card number must contain 16 digits");
      return false;
   }
   else {
      return true;
   }
}

 

Note that this assumes that the proper pattern for cardNum is simply a string of 16 digits without hyphens or spaces.