最佳答案
http://en.wikipedia.org/wiki/Luhn_algorithm
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);
}