Codecademy export

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:
function validateCard(cardToCheck) {
  let length = cardToCheck.length-1;
  let sum = 0;
  let checker = [];
  
  for(let i  = length; i >= 0; i-- ){    
    //console.log(i);
    if ((length-i)%2!=0) {
      let double = cardToCheck[i] * 2;
      //console.log(cardToCheck[i]);
      if (double > 9) 
        double -= 9;
      sum += double;
      //console.log(double);
      //console.log(sum);
      //console.log('____________!');
    }
    else {
      sum += cardToCheck[i];
      //console.log(cardToCheck[i]);
      //console.log(sum);
      //console.log('____________');
    }
  } 
  //console.log(sum);
  if (sum%10 == 0) return(true);
  else return(false);  
}

function findInvalidCards(cardsSetToCheck){
  let invalidCards = [];
  for (let i = 0; i < cardsSetToCheck.length; i++)    
    if (!validateCard(cardsSetToCheck[i]))
        invalidCards.push(cardsSetToCheck[i]);  
  return invalidCards;
}

function invalidCardCompanies(invalidCards) {
  let companies = ['Company not found',
                   'Company not found',
                   'Company not found',
                   'Amex (American Express)',
                   'Visa',
                   'Mastercard',
                   'Discover',
                   'Company not found',
                   'Company not found',
                   'Company not found'];
  let companyCodeFound = [0,0,0,0,0,0,0,0,0,0];
  let result = [];
  for (let i = 0; i < invalidCards.length; i ++) {
    let codeFound = invalidCards[i][0];
    console.log(codeFound);
    
    if (companyCodeFound[codeFound] == 0)
    {
      result.push(companies[codeFound]);
      companyCodeFound[codeFound] = 1;
    }
  }
  return result;
}

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

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

console.log(invalidCardCompanies(findInvalidCards(batch)).join('\n'));

Thank you, this helps.