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]

// 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:
const validateCred = (array) => {
    const testArray = array;
    for(let i = testArray.length-1;i>=0;i--){
        if(i%2==0){
            if(testArray[i]*2 > 9){
                testArray[i] = testArray[i]*2-9
            }else{
                testArray[i] = testArray[i]*2
            }
        }
       
    }

    const arraySum = testArray.reduce((acc,current) => acc+current)

    return arraySum%10 === 0;
}


const findInvalidCards = (nestedArray) => {
    const invalidCards = []
    for(const array of nestedArray){
        const isValid = validateCred(array);

        if(!isValid){
            invalidCards.push(array);
        }
    }

    return invalidCards;
}



const idInvalidCardCompanies = (nestedArray) => {
    let invalidCardsCompanies = []
    for(let array of nestedArray){
        switch (array[0]){
            case 3 :
                invalidCardsCompanies.push('Amex (American Express)');
            break;
            case 4 :
                invalidCardsCompanies.push('Visa');
            break;
            case 5 :
                invalidCardsCompanies.push('Mastercard');
            break;
            case 6 :
                invalidCardsCompanies.push('Discover');
            break;
            default:
                console.log(`${array[0]} - Company not found`);
            break;
        }
       
    }
    invalidCardsCompanies =  [...new Set(invalidCardsCompanies)];

    return invalidCardsCompanies;
}


console.log(idInvalidCardCompanies(findInvalidCards(batch)))