Credit Card Validation.

Mod10 Check tutorial

	Mod 10 Check Example and Tutorial																SUM
STEP 1	4	0	1	1	5	0	1	0	3	6	8	5	3	3	3	7
STEP 2	8	0	2	1	10	0	2	0	6	6	16	5	6	3	6	7
STEP 3	8	0	2	1	1+0	0	2	0	6	6	1+6	5	6	3	6	7
STEP 4	8	0	2	1	1	0	2	0	6	6	7	5	6	3	6	7	60
	EXPLANATION
STEP 1	Write the no to be mod 10 checked
STEP 2	Double every 2nd digit from the Right last
STEP 3	Sum=60 Add the double and make it single digit and then add all the digit
STEP 4	If the result eg.60 is in muliples of 10 then its Valid.

Javascript For Credit Card Validation

function Mod10(ccNumb) {  // v2.0

            var valid = "0123456789"  // Valid digits in a credit card number

            var len = ccNumb.length;  // The length of the submitted cc number

            var iCCN = parseInt(ccNumb);  // integer of ccNumb

            var sCCN = ccNumb.toString();  // string of ccNumb

            sCCN = sCCN.replace(/^\s+|\s+$/g, '');  // strip spaces

            var iTotal = 0;  // integer total set at zero

            var bNum = true;  // by default assume it is a number

            var bResult = false;  // by default assume it is NOT a valid cc

            var temp;  // temp variable for parsing string

            var calc;  // used for calculation of each digit

            // Determine if the ccNumb is in fact all numbers

            for (var j = 0; j < len; j++) {

                temp = "" + sCCN.substring(j, j + 1);

                if (valid.indexOf(temp) == "-1") { bNum = false; }

            }

// if it is NOT a number, you can either alert to the fact, or just pass a failure

            if (!bNum) {

 /*alert("Not a Number");*/
                bResult = false;

            }

            // Determine if it is the proper length

            if ((len == 0) && (bResult)) {  
// nothing, field is blank AND passed above # check

                bResult = false;

            } else {  
// ccNumb is a number and the proper length - let's see if it is a valid card number

                if (len >= 15) {  // 15 or 16 for Amex or V/MC

                    for (var i = len; i > 0; i--) {  // LOOP throught the digits of the card

                        calc = parseInt(iCCN) % 10;  // right most digit

                        calc = parseInt(calc);  // assure it is an integer

                        iTotal += calc;  
// running total of the card number as we loop - Do Nothing to first digit

                        i--;  
// decrement the count - move to the next digit in the card

                        iCCN = iCCN / 10;                               
// subtracts right most digit from ccNumb

                        calc = parseInt(iCCN) % 10;    
// NEXT right most digit

                        calc = calc * 2;                                 
// multiply the digit by two

/* Instead of some screwy method of converting 16 to a string and then parsing 1 and 6 and then adding them to make 7,*/

// I use a simple switch statement to change the value of calc2 to 7 if 16 is the multiple.

                     switch (calc) {

                         case 10: calc = 1; break;       //5*2=10 & 1+0 = 1

                         case 12: calc = 3; break;       //6*2=12 & 1+2 = 3

                         case 14: calc = 5; break;       //7*2=14 & 1+4 = 5

                         case 16: calc = 7; break;       //8*2=16 & 1+6 = 7

                         case 18: calc = 9; break;       //9*2=18 & 1+8 = 9

                         default: calc = calc;//4*2= 8 &   8 = 8  -same for all lower numbers

                        }

                        iCCN = iCCN / 10;  // subtracts right most digit from ccNum

                        iTotal += calc;  // running total of the card number as we loop

                    }  // END OF LOOP

                    if ((iTotal % 10) == 0) {  // check to see if the sum Mod 10 is zero

                        bResult = true;  // This IS (or could be) a valid credit card number.

                    } else {

                        bResult = false;  // This could NOT be a valid credit card number

                    }

                }

            }

            // change alert to on-page display or other indication as needed.

            // if(bResult) {

            // alert("This IS a valid Credit Card Number!");

            // }

            // if(!bResult){

            // alert("This is NOT a valid Credit Card Number!");

            // }

            return bResult; // Return the results

        }