Update 3.js

Author: Ayogit1

Sprint-1/2-mandatory-errors/3.js

@@ -7,3 +7,6 @@ const last4Digits = cardNumber.slice(-4);
 // Then run the code and see what error it gives.
 // Consider: Why does it give this error? Is this what I predicted? If not, what's different?
 // Then try updating the expression last4Digits is assigned to, in order to get the correct value
+
+const cardNumber2 = String(cardNumber);
+const last4Digits = cardNumber2.slice(-4);