Implement credit card validator for Sprint 3 stretch coursework

Author: Richiealx

Sprint-3/4-stretch/card-validator.js

@@ -0,0 +1,14 @@
+function validateCreditCard(number) {
+  if (number.length !== 16 || !/^\d+$/.test(number)) return false;
+  const uniqueDigits = new Set(number);
+  if (uniqueDigits.size < 2) return false;
+  const lastDigit = parseInt(number[number.length - 1], 10);
+  if (lastDigit % 2 !== 0) return false;
+  const sum = number.split('').reduce((acc, digit) => acc + parseInt(digit, 10), 0);
+  if (sum <= 16) return false;
+  return true;
+}
+
+console.log(validateCreditCard('9999777788880000')); // true
+console.log(validateCreditCard('4444444444444444')); // false
+console.log(validateCreditCard('6666666666666661')); // false