codeCademy_ChallengeProject_CreditCardChecker.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 => {
  let checkDigit = array[array.length-1];
  let sum = checkDigit;
  for(let i= array.length -2; i >= 0; i-=2) {
    /*loop en reversa... let i= array.length -2, para comenzar en el penúltimo elemento. i >= 0, para incluir el primer elemento.  i-=2, para intecalar entre índices */ 
       let check2 = array[i] * 2;
    if(check2 > 9){
      check2-=9;

    }
     sum +=check2;
  }

  for(let i= array.length -3; i >= 0; i-=2){
    /*loop en reversa...let i= array.length -3, para comenzar en el antepenúltimo elemento. i >= 0, para incluir el primer elemento.  i-=2, para intecalar entre índices */ 
    sum +=array[i];
  }
  if (sum % 10 === 0){
      return true;
    } else {
      return false;
    }
};

const findInvalidCards = nestedArray => {
  let invalidCard = [];
  for(array of nestedArray) {
    if(validateCred(array)!== true){
      invalidCard.push(array);
    }
}
return invalidCard;
};

const idInvalidCardCompanies = nestedArray => {
  let companies = [];
  let onlyCompanies = [];
  for(array of nestedArray){
    switch (array[0]) {
      case 3:
      companies.push('Amex');
      break;
      case 4:
      companies.push('Visa');
      break;
      case 5:
      companies.push('Mastercard');
      break;
      case 6:
      companies.push('Discover');
      break;
      default:
      companies.push('Company not found');
    }
    /*la siguiente función filtra la variable companies para que solo haya una instancia (NO se repitan) de cada compañía en la variable final que se retorna, onlyCompanies*/
    onlyCompanies = companies.filter((item,
        index) => companies.indexOf(item) === index);
  }
return onlyCompanies;
};

let test = findInvalidCards(batch);
console.log(idInvalidCardCompanies([invalid2]));