# Credit Card Checker (small error remains)

I know, I know, this is not pretty, but it kind of works. I’m a newb.

The only thing left that really bugs me is the idInvalidCardCompanies that prints ‘Company not found’ 3 times despite invalidCards not containing any numbers starting with 3, 4, 5, or 6. Can anyone explain where the problem is?

// 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(array) {
var total = 0
for (let i = array.length - 1; i >= 0; i–) {
if (array.length % 2 === 0) {
if ([i] % 2 === 0) {
if (array[i] * 2 > 9) {
total += array[i] * 2 - 9
} else {
total += array[i] * 2
}
} else {
total += array[i]
}
}

``````  if (array.length % 2 === 1) {
if ([i] % 2 === 1) {
if (array[i] * 2 > 9) {
total += array[i] * 2 - 9
} else {
total += array[i] * 2
}
} else {
total += array[i]
}
}
``````

} if (total % 10 === 0) {
return true
} else {
return false
}
}

const invalidCards =
const findInvalidCards = (nestedArr) => {
for (let i = 0; i < nestedArr.length; i++) {
if (validateCred(nestedArr[i]) === false) {
invalidCards.push(nestedArr[i])
}
}
}
findInvalidCards(batch)

const invalidCardCompanies =
const idInvalidCardCompanies = (invalidCards) => {
for (let i = 0; i < invalidCards.length; i++) {
if (invalidCardCompanies.indexOf(‘Amex’) === -1 && invalidCards[i][0] === 3) {
invalidCardCompanies.push(‘Amex’)
} else if (invalidCardCompanies.indexOf(‘Visa’) === -1 && invalidCards[i][0] === 4) {
invalidCardCompanies.push(‘Visa’)
} else if (invalidCardCompanies.indexOf(‘Mastercard’) === -1 && invalidCards[i][0] === 5) {
invalidCardCompanies.push(‘Mastercard’)
} else if (invalidCardCompanies.indexOf(‘Discover’) === -1 && invalidCards[i][0] === 6) {
invalidCardCompanies.push(‘Discover’)
} else if (invalidCards[i][0] !== 3 && 4 && 5 && 6) {
}
}
}

idInvalidCardCompanies(invalidCards)

Is it also returning the invalid card companies list properly?

Yes it does! When I call findInvalidCards(batch) it correctly returns the invalid cards to invalidCards.

To preserve code formatting in forum posts, see: [How to] Format code in posts

``````else if (invalidCards[i][0] !== 3 && 4 && 5 && 6) {
``````

is equivalent to

``````else if ((invalidCards[i][0] !== 3) && (4) && (5) && (6)) {
``````

If we look at the documentation for JavaScript Operator Precedence Table , we can see that the inequality operator has a higher precedence than the logical `&&`.

In the current form, your condition is only comparing `invalidCards[i][0]` with `3`. The rest of the operands (the numbers `4` and `5` and `6`) are already truthy.

1 Like

Thank you!! That makes sense