function luhnCheckSum(){
      sCardNum
      var iOddSum = 0;
      var iEvenSum = 0;
      var bIsOdd = true;
      for(var i=sCardNum.length-1; i>=0; i--){
         var iNum = parseInt(sCardNum.charAt(i));
         if(bIsOdd){
            iOddSum +=iNum;
         }else{
            iNum = Inum*2;
            if(iNum > 9){
               iNum = eval(iNum.toSring.split("").join("+"));
            }
            iEvenSum += iNum;
         }
         bIsOdd = !bIsOdd;
      }
   } 
//javascript/7088