Credit Card Checker

Hey Guys,

This project took me a while, so I just thought I would share my code with everyone! Extensive commenting to explain lol. Thanks in advance!

``````// 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,
];

const validateCred = (card) => {
// Implement Luhn's Algorithm
// If you don't use .slice() here to make a copy, you will be mutating the original array (i.e. do not use let newArray = card)
let cardArray = card.slice();
let sum = 0;
let checkDigit = cardArray.pop();

// Step 1: Reverse the array
cardArray = cardArray.reverse();

// Step 2: Iterate through the array and double every other number.  If it is greater than 9, subtract 9
for (let i = 0; i < cardArray.length; i++) {
cardArray[i] *= 2;
if (cardArray[i] > 9) {
cardArray[i] -= 9;
}
i++;
}

// Step 3: Iterate through the new array and add each element to the sum
cardArray.forEach((num) => {
sum += num;
});

// Step 4: Add the check digit to the sum
sum += checkDigit;

// Step 5: If our sum is evenly divisible by 10, it is valid.  Otherwise, it is invalid
if (sum % 10 === 0) {
return true;
} else {
return false;
}
};

// This algorithm will find invalid cards and give you and array of the cards.
const findInvalidCards = (cards) => {
let invalidCards = [];
// loop through the array and add invalid cards to the invalid array
cards.forEach((card) => {
if (!validateCred(card)) {
invalidCards.push(card);
}
});

return invalidCards;
};

// Adds the name of the credit company that sent out an invalid card, without duplicates
const idInvalidCardCompanies = (cards) => {
let companyArray = [];

// iterate through the invalid array and check which card matches what company by matching the first digit.

// concerning indexOf().  This function will return -1 if a value does not exist in the array.
cards.forEach((card) => {
switch (card[0]) {
case 3:
if (companyArray.indexOf("Amex (American Express)") === -1) {
companyArray.push("Amex (American Express)");
}
break;
case 4:
if (companyArray.indexOf("Visa") === -1) {
companyArray.push("Visa");
}
break;
case 5:
if (companyArray.indexOf("Mastercard") === -1) {
companyArray.push("Mastercard");
}
break;
case 6:
if (companyArray.indexOf("Discover") === -1) {
companyArray.push("Discover");
}
break;
default: