Build up a function to validate credit card

Author: Fares-Bakhet

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

@@ -0,0 +1,46 @@
+function validateCreditCard(cardNumber) {
+  const numStr = cardNumber.toString();
+
+  if (numStr.length !== 16) {
+    return false;
+  } // Number must be 16 digits.
+
+  const uniqueDigits = new Set(numStr);
+  if (uniqueDigits.size < 2) {
+    return false;
+  } // Must have at least two different digits.
+
+  const lastDigit = Number(numStr[numStr.length - 1]);
+  if (lastDigit % 2 !== 0) {
+    return false;
+  } // Last digit must be even.
+
+  let sum = 0;
+  for (let char of numStr) {
+    sum += Number(char);
+  } // Sum of all digits must be greater than 16.
+
+  if (sum <= 16) {
+    return false;
+  } // Sum check
+
+  return true;
+}
+
+// Test cases:
+
+// Number must be 16 digits
+console.log(validateCreditCard(9999)); // false
+console.log(validateCreditCard(9999888877776662)); // true
+
+// Must have at least two different digits
+console.log(validateCreditCard(1111111111111111)); // false
+console.log(validateCreditCard(1234567890123456)); // true
+
+// Last digit must be even
+console.log(validateCreditCard(1234567890123451)); // false
+console.log(validateCreditCard(1234567890123452)); // true
+
+// Sum of all digits must be greater than 16
+console.log(validateCreditCard(1111111111111110)); // false
+console.log(validateCreditCard(1234567890123456)); // true