Implement credit card validator function

Author: HoussamLh

Sprint-3/4-stretch-investigate/password-validator.js

@@ -1,6 +1,48 @@
-function passwordValidator(password) {
-    return password.length < 5 ? false : true
+function isValidCreditCard(cardNumber) {
+  // Check if cardNumber is exactly 16 characters and all are digits
+  if (!/^\d{16}$/.test(cardNumber)) {
+    return false;
+  }
+
+  // Check if card has at least two different digits
+  if (/^(\d)\1{15}$/.test(cardNumber)) {
+    return false;
+  }
+
+  // Check if last digit is even
+  const lastDigit = Number(cardNumber[15]);
+  if (lastDigit % 2 !== 0) {
+    return false;
+  }
+
+  // Calculate the sum of all digits and check if greater than 16
+  const sum = cardNumber.split('').reduce((acc, digit) => acc + Number(digit), 0);
+  if (sum <= 16) {
+    return false;
+  }
+
+  // All conditions passed, card is valid
+  return true;
 }
 
+// Example usage:
+// console.log(isValidCreditCard("9999777788880000")); // true
+// console.log(isValidCreditCard("4444444444444444")); // false
+
+module.exports = isValidCreditCard;
+
+/* 
+
+Explanation:
+
+The first if uses a regular expression to ensure the card number is exactly 16 digits long and contains only digits.
+
+The second if uses a regex to check if all digits are the same (e.g., all '4's).
+
+Then, we check if the last digit is even using modulo %.
+
+Then, we calculate the sum of all digits with reduce and ensure it is greater than 16.
+
+Finally, we return true if all these checks pass, else false.
 
-module.exports = passwordValidator;
+*/