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