card-validator.md.js updated

Author: Fithi-Teklom

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

@@ -0,0 +1,59 @@
+/**
+ * Validates a credit card number based on specific rules:
+ * - Must be 16 digits
+ * - Must have at least two different digits
+ * - Final digit must be even
+ * - Sum of all digits must be greater than 16
+ * 
+ * @param {string} cardNumber - The credit card number to validate
+ * @returns {boolean} - true if valid, false if invalid
+ */
+function validateCreditCard(cardNumber) {
+    // Rule 1: Check if length is exactly 16 digits and all are numbers
+    if (!/^\d{16}$/.test(cardNumber)) {
+        return false;
+    }
+
+    // Convert string to array of numbers
+    const digits = cardNumber.split('').map(Number);
+
+    // Rule 2: Check for at least two different digits
+    const uniqueDigits = new Set(digits);
+    if (uniqueDigits.size < 2) {
+        return false;
+    }
+
+    // Rule 3: Check if the final digit is even
+    if (digits[digits.length - 1] % 2 !== 0) {
+        return false;
+    }
+
+    // Rule 4: Check if sum of all digits is greater than 16
+    const sum = digits.reduce((acc, val) => acc + val, 0);
+    if (sum <= 16) {
+        return false;
+    }
+
+    // All rules passed
+    return true;
+}
+
+// Example usage:
+console.log(validateCreditCard("9999777788880000")); // true
+console.log(validateCreditCard("6666666666661666")); // true
+console.log(validateCreditCard("a92332119c011112")); // false
+console.log(validateCreditCard("4444444444444444")); // false
+console.log(validateCreditCard("1111111111111110")); // false
+console.log(validateCreditCard("6666666666666661")); // false
+
+module.exports = validateCreditCard;
+
+const validateCreditCard = require('./credit-card-validator');
+
+test("valid credit card number", () => {
+    expect(validateCreditCard("9999777788880000")).toBe(true);
+});
+
+test("invalid credit card number (all same digits)", () => {
+    expect(validateCreditCard("4444444444444444")).toBe(false);
+});