3.js

const cardNumber = 4533787178994213;
//const last4Digits = cardNumber.slice(-4);

const last4Digits = cardNumber.toString().slice(-4);


console.log(last4Digits);

// 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

// I think the code does not work because cardNumber variable is not stored as string.

// My guess was right. 

// Therefore first we need to change CardNumber variable into string before we use the slice method.