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:

const validateCred = arr => {
  //return true when valid, false if invalid
  //does not mutate original
  let testArr = [];

//1. iterate backwards
for (let i = (arr.length - 1); i >= 0; i--) {
  //2. every other digit is doubled
  if (i % 2 !== 0) {
    testArr.unshift(arr[i]);
  } else {
    //2.5 if after doubling, > 9, subtract 9
    if ((arr[i] * 2) <= 9) {
      testArr.unshift(arr[i] * 2);
    } else {
      testArr.unshift((arr[i] * 2) - 9);
    }
  }
}
//3. sum up all the digits
testArr = testArr.reduce((previousValue, currentValue) => previousValue + currentValue);

//4. if sum modulo 10 is 0 = valid
return testArr % 10 === 0 ? true : false;
}


const findInvalidCards = arr => {
  let invalidCards = [];
  for (let i = 0; i < arr.length; i++) {
    if (validateCred(arr[i])) {
      continue
    } else {
      invalidCards.push(arr[i]);
    }
  }
  return invalidCards;
}


const idInvalidCardCompanies = arr => {
  let companies = [];

  for (let i = 0; i < arr.length; i++) {
    switch (true) {
      case arr[i][0] === 3 :
        if (companies.indexOf('Amex (American Express)') === -1) {
          companies.push('Amex (American Express)')
        }
        break;
      case arr[i][0] === 4 : 
        if (companies.indexOf('Visa') === -1) {
          companies.push('Visa')
        }
        break;
      case arr[i][0] === 5 :
        if (companies.indexOf('Mastercard') === -1) {
          companies.push('Mastercard')
        }
        break;
      case arr[i][0] === 6 :
        if (companies.indexOf('Discover') === -1) {
          companies.push('Discover')
        }
        break;
      default :
        console.log('Company not found')
    }
  }

  return companies;
}

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