# Challenge Project: Credit Card Checker

Hi, everyone! Being new to programming, I would greatly appreciate your feedback on my code. Could you please take a moment to review and offer any corrections or suggestions?

Credit Card Project

// 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(numArr) {
let toValidate = 0;
for (let i = numArr.length - 1; i >= 0; i–) {
let currentValue = numArr[i]
if ((numArr.length - 1 - i) % 2 === 1) {
currentValue *= 2;
if (currentValue > 9){
currentValue -= 9;
}
}
toValidate += currentValue;
}
}
// test:
console.log(validateCred(invalid2));
console.log(validateCred(valid2));

function findInvalidCards(cards) {
const invalids =

``````for (let i = 0; i < cards.length; i++) {
let cred = cards[i];
if (!validateCred(cred)) {
invalids.push(cred);
}
}
return invalids;
``````

}
//test:
console.log(findInvalidCards([valid1, valid2, valid3, valid4, valid5]));
console.log(findInvalidCards([invalid1, invalid2, invalid3, invalid4, invalid5]));
console.log(findInvalidCards(batch));

function idInvalidCardCompanies(invalid) {
const companies = ;
for (let i = 0; i < invalid.length; i++) {
switch (invalid[i][0]){
case 3:
if (companies.indexOf(‘Amex’) === -1) {
companies.push(‘Amex’);
}
break
case 4:
if (companies.indexOf(‘Visa’) === -1) {
companies.push(‘Visa’);
}
break
case 5:
if (companies.indexOf(‘Mastercard’) === -1) {
companies.push(‘Mastercard’);
}
break
case 6:
if (companies.indexOf(‘Discover’) === -1) {
companies.push(‘Discover’);
}
break
default: