main.js

// 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]
const testNum = [4, 5, 3, 9, 6, 8, 9, 8, 8 ,7, 7, 0, 5, 7, 9, 8];

// 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]


// Add your functions below:
function validateCred(array) {
    let check = false;
    let checkSum = 0;

    // Start at second last digit and then every other digit 
    for (let i = array.length - 2; i >= 0; i -= 2) {
        let doubleValue = array[i] * 2;
        // console.log(doubleValue);
        // console.log(`i is ${i}`);
        // console.log(array[i]);
        
        if (doubleValue > 9 ) {
            checkSum += doubleValue - 9; 
        } else {
            checkSum += doubleValue;
        }
    }

    // Start at last digit then every other digit
    for (let i = array.length - 1; i >=0 ; i -= 2) {
        checkSum += array[i];
    }

    if (checkSum % 10 == 0){
        check = true;
    }
    return check;
}

function findValidCards(array) {
    let invalidArrays = [];

    // filter with anonymous arrow function which reverses 
    // the call of the validateCred function get only invalid numbers
    invalidArrays = array.filter((arr) => !validateCred(arr)); 
    return invalidArrays;
}


function idInvalidCardCompanies(array) {
    let cardCompanies = [];
    let singleCompanies = [];
    for (let i = 0; i < array.length; i++){
        // console.log(array[i][0]);
        console.log(array[i]);
        if (array[i][0] == 3){
            cardCompanies.push("Amex");
        } else if (array[i][0] == 4) {
            cardCompanies.push("Visa");
        } else if (array[i][0] == 5) {
            cardCompanies.push("Mastercard");
        } else if (array[i][0] == 6) {
            cardCompanies.push("Discover");
        } else {
            // console.log("Company not found.");
        }
    }

    // If item doesn't exist, push to array
    cardCompanies.forEach(function(item) {
        if(singleCompanies.indexOf(item) < 0) {
            singleCompanies.push(item);
        }
    })
    return singleCompanies;
}



// console.log(validateCred(mystery1));
// validateCred(testNum);

// console.log(findValidCards(batch));
let invalidNum = findValidCards(batch);
// console.log(invalidNum);

console.log(idInvalidCardCompanies(batch));