Fix last4Digits extraction from cardNumber

Updated last4Digits assignment to correctly extract the last 4 digits of cardNumber.

Author: cywong-dev

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

@@ -1,9 +1,14 @@
 const cardNumber = 4533787178994213;
-const last4Digits = cardNumber.slice(-4);
+//const last4Digits = cardNumber.slice(-4);
 
 // The last4Digits variable should store the last 4 digits of cardNumber
 // However, the code isn't working
 // Before running the code, make and explain a prediction about why the code won't work
 // 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
+
+// [ChunYanWong] The slice method extract substring starting with the first parameter position
+// There is no -4 starting position and hence it will not work
+
+const last4Digits = cardNumber.slice(cardNumber.length - 4)