function Mod10(ccNumb)
{
    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)
    {
        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
            }
            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
            }
        }
    }
    return bResult;
}