/*---------------------------------------------------------------*/
/*                                                               */
/* Function  : isCreditCard()                                           */
/* Purpose   : Check if cc is LUHN10      */
/*                                                                  */
/*                                                               */
/* Parameters:     cc - the cc number                                                       */
/*                                                               */
/* Returns   : boolean                                              */
/*                                                               */
/* Usage     : isCreditCard(cc)                                           */
/*---------------------------------------------------------------*/
 
     function isCreditCard( CC ) 
     {                         
          if (CC.length > 19)
               return (false);
 
          sum = 0; mul = 1; l = CC.length;
          for (i = 0; i < l; i++) 
          {
               digit = CC.substring(l-i-1,l-i);
               tproduct = parseInt(digit ,10)*mul;
               if (tproduct >= 10)
                    sum += (tproduct % 10) + 1;
               else
                    sum += tproduct;
               if (mul == 1)
                    mul++;
               else
                    mul--;
          }
          if ((sum % 10) == 0)
               return (true);
          else
               return (false);
     }