# Challenge Project: Credit Card Checker | Feedback appreciated

Hi Everyone,

This is my first time posting anything on Codecademy Forums.
Is there anything that I may improve on this code? I hope you share your thoughts on my code.

``````// 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];

// Array of 4 accepted companies which each have unique first digits assigned.
const companies = [
{firstDigit: 3, cName: 'Amex (American Express)'},
{firstDigit: 4, cName: 'Visa'},
{firstDigit: 5, cName: 'Mastercard'},
{firstDigit: 6, cName: 'Discover'}
];

//console.log(companies[2].cName);

//----------------------------------------------------------------------------\\

const validateCred = arr => {

let lastIndexNumber = arr.length-1;
let sumOfEvens = 0;
let sumOfOdds = 0;
//Sums of Even digits and Odd digits of the selected array(arr)

if (lastIndexNumber % 2 === 0) {
for (let i = lastIndexNumber; i >= 0; i--) {
if (i % 2 === 0)    {sumOfEvens += arr[i];
}
else {
if (arr[i] < 5) {sumOfOdds += arr[i]*2;}
else {sumOfOdds += arr[i]*2-9}
}
}
}

else {
for (let j = lastIndexNumber; j >= 0; j--) {
if (j % 2 === 1){
sumOfOdds += arr[j];
}
else {
if (arr[j] < 5) {sumOfEvens += arr[j]*2;}
else {sumOfEvens += arr[j]*2-9}
}
}
}

let sumOfEvensAndOdds = sumOfEvens + sumOfOdds;
//Luhn algoritmasını test edebilmek üzere rakamların toplandığı değişken.

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

};

//console.log(validateCred(valid3));

const findInvalidCards = arr => {
let invalidCardsDeck = [];

for(let i = 0; i < arr.length; i++) {
if(validateCred(arr[i]) === false){
invalidCardsDeck.push(arr[i]);
}
}
return invalidCardsDeck;
};

//console.log(findInvalidCards(batch));

const invalidCardCompanies = arr => {
let invalidCards = findInvalidCards(arr);
let listOfInvalidCompanies = [];

for(let i = 0; i < invalidCards.length; i++) {

for(let j = 0; j < companies.length; j++){
if (invalidCards[i][0] === companies[j].firstDigit){
listOfInvalidCompanies.push(companies[j].cName);
}
}
}

let uniqueList = [...new Set(listOfInvalidCompanies)];

return uniqueList;

};

//console.log(invalidCardCompanies(batch));

``````

Thank you,
ZeePLA.