Completed credit-card-validator exercise

Author: anosidium

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

@@ -0,0 +1,30 @@
+function creditCardValidator(cardNumber) {
+  // Check that the card number contains numbers only
+  if (isNaN(cardNumber)) return false;
+
+  // Convert the card number to a string so we can check its digits easily
+  let cardNumberString = String(cardNumber);
+
+  // Check that the card number has exactly 16 digits
+  if (cardNumberString.length != 16) return false;
+
+  // Check that the last digit is even
+  if (cardNumberString[15] % 2 != 0) return false;
+
+  // Calculate the sum of all digits
+  const sum = cardNumberString
+    .split("")
+    .reduce((sum, digit) => (sum += Number(digit)), 0);
+
+  // If the sum of all digits is 16 or less, the card is invalid
+  if (sum <= 16) return false;
+
+  // Use Set to filter out duplicate digits
+  let uniqueDigits = new Set(cardNumberString);
+
+  // Make sure the card number isn’t made up of all the same digit
+  if (uniqueDigits.size < 2) return false;
+
+  // If all conditions pass, the card number is valid
+  return true;
+}