// Credit Card Validation Javascript
// copyright 12th May 2003, by Stephen Chapman, Felgall Pty Ltd

// You have permission to copy and use this javascript provided that
// the content of the script is not changed in any way.

function validateCreditCard(s) {
var v = "0123456789";
var w = "";
for (var i=0; i < s.length; i++) {
x = s.charAt(i);
if (v.indexOf(x,0) != -1)
w += x;
}
var j = w.length / 2;
if (j < 6.5 || j > 8 || j == 7) return false;
var k = Math.floor(j);
var m = Math.ceil(j) - k;
var c = 0;
for (var i=0; i<k; i++) {
a = w.charAt(i*2+m) * 2;
c += a > 9 ? Math.floor(a/10 + a%10) : a;
}
for (var i=0; i<k+m; i++) c += w.charAt(i*2+1-m) * 1;
return (c%10 == 0);
}