# Credit Card Checker Project

Hi,

I’ve been playing around with the Credit Card Checker for a few days now, and it is starting to hurt my brain!! I managed to get the validateCred function to work, but when I attempt the second part it comes up with the error “TypeError: arr.slice is not a function at validateCred”.

Total newbie, so any help is appreciated!!

Thanks

``````// All valid credit card numbers
const valid1 = [4, 5, 3, 9, 6, 7, 7, 9, 0, 8, 0, 1, 6, 8, 0, 8];
const valid2 = [5, 5, 3, 5, 7, 6, 6, 7, 6, 8, 7, 5, 1, 4, 3, 9];
const valid3 = [3, 7, 1, 6, 1, 2, 0, 1, 9, 9, 8, 5, 2, 3, 6];
const valid4 = [6, 0, 1, 1, 1, 4, 4, 3, 4, 0, 6, 8, 2, 9, 0, 5];
const valid5 = [4, 5, 3, 9, 4, 0, 4, 9, 6, 7, 8, 6, 9, 6, 6, 6];

// All invalid credit card numbers
const invalid1 = [4, 5, 3, 2, 7, 7, 8, 7, 7, 1, 0, 9, 1, 7, 9, 5];
const invalid2 = [5, 7, 9, 5, 5, 9, 3, 3, 9, 2, 1, 3, 4, 6, 4, 3];
const invalid3 = [3, 7, 5, 7, 9, 6, 0, 8, 4, 4, 5, 9, 9, 1, 4];
const invalid4 = [6, 0, 1, 1, 1, 2, 7, 9, 6, 1, 7, 7, 7, 9, 3, 5];
const invalid5 = [5, 3, 8, 2, 0, 1, 9, 7, 7, 2, 8, 8, 3, 8, 5, 4];

// Can be either valid or invalid
const mystery1 = [3, 4, 4, 8, 0, 1, 9, 6, 8, 3, 0, 5, 4, 1, 4];
const mystery2 = [5, 4, 6, 6, 1, 0, 0, 8, 6, 1, 6, 2, 0, 2, 3, 9];
const mystery3 = [6, 0, 1, 1, 3, 7, 7, 0, 2, 0, 9, 6, 2, 6, 5, 6, 2, 0, 3];
const mystery4 = [4, 9, 2, 9, 8, 7, 7, 1, 6, 9, 2, 1, 7, 0, 9, 3];
const mystery5 = [4, 9, 1, 3, 5, 4, 0, 4, 6, 3, 0, 7, 2, 5, 2, 3];

// An array of all the arrays above
const batch = [valid1, valid2, valid3, valid4, valid5, invalid1, invalid2, invalid3, invalid4, invalid5, mystery1, mystery2, mystery3, mystery4, mystery5];

function validateCred(arr) {
let array = arr.slice();
for (let i = (array.length - 2); i >= 0; i = i - 2) {
array[i] = array[i] * 2;
if (array[i] > 9) {
array[i] = array[i] - 9;
}
}
let arraySum = array.reduce((acc, cur) => acc + cur);
if (arraySum % 10 === 0) {
return true
} else {
return false
}
};
console.log(validateCred(mystery1));

function findInvalidCards(cards) {
let invalidCard = [];
let validCard = [];
for (let i=0; i=cards.length; i++) {
if (cards = validateCred(true)){
validCard.push
} else {
invalidCard.push
}
}
};

console.log(findInvalidCards(batch))
``````

Your issue is this part here. Firstly, that should be `==` or `===` to do a comparison, currently it is overwriting the `cards` variable. Secondly, you are calling `validateCred()` with the value of `true`. This argument needs to be an array for `validateCred()` to work. What you have currently is `if true is a valid card, and equal to cards then...`. What you should have is `if cards[i] is a valid card then...`.

Hey I’m assuming you figured out the solution, I am getting the same error as you were and I doubt you remember exactly what you did but if you can, please help thank you!

``````validateCred = arr => {
const len = arr.length
const parity = len % 2
let sum = 0
for (var i = len-1; i>=0; i--){
let dub = parseInt(arr[i])
if (i % 2 === parity) {dub *= 2}
if (dub > 9) {dub - 9}
sum += dub
}     return sum % 10
}

findInvalidCards = card => {
let invalidCard = []
let validCard = []
for (let i=0; i=card.length; i++){
if (card[i] === validateCred()){
validCard.push
} else if (card[i] != validateCred){
invalidCard.push
}
}
}
validateCred(valid1)
console.log(validateCred(valid1))
console.log(findInvalidCards(batch))
``````

The reason you are getting the error is because in

it is trying to call the function `validateCred()` without an argument, instead of passing in an array (card) to be validated. I believe there are a few issues with how your `validateCred()` function works as it appears to be returning ‘7’ on a valid card, which should be 0 if it is valid, so have another look at that.

1 Like

ah ok. Thank you very much for the reply!

Let me know how you get on and ask if you need any more help!