Codecademy Project: The Luhn algorithm is a series of mathematical calculations used to validate certain identification numbers, e.g. credit card numbers. The calculations in the Luhn algorithm can be broken down as the following steps: Starting from the farthest digit to the right, AKA the check digit, iterate to the left. As you iterate to the…

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 = arr => {
  let endEl = 0;
  let multiEl = 0;
  let normEl = 0;
  let sum = 0;
  let sliceArr = arr.slice()
  let revArr = sliceArr.reverse();

sum = revArr.forEach((value, index) => {
  if(index == 0){
    endEl = value
  } else if( index % 2 == 0) {
    normEl += value;
  } else if(value * 2 > 9) {
    multiEl += (value * 2 -9);
  } else {
    multiEl += value * 2;
  }

})

sum = normEl + multiEl + endEl
//return sum

//console.log("Sum is: "+ sum)
   if(sum % 10 === 0) {
     return true;
     } else {
     return false
     }; 
}

const testThem = (array, func) => {
  array.forEach(item => {
    //func(item);
    console.log(func(item))
    return func(item)
  })
};

//console.log(testThem(batch,validateCred))
//console.log(validateCred(valid1));
const invalidCards = []
const findInvalidCards = arr => {
  //let invalidCards = [];
  let result;
  arr.forEach(array => {
    result = validateCred(array);
    if( result === false) {
      invalidCards.push(array);
    }
    
  })
  //console.log(invalidCards);
  return invalidCards
}
findInvalidCards(batch);
//console.log(invalidCards)

const idInvalidCardCompanies = arr => {
  const companies = [];
  let firstNum;
  let companyName;
  //use switch here...
  arr.forEach(array => {
    firstNum = array[0];
    switch (firstNum) {
      case 3:
      companyName = "Amex (American express)";
      break;
      case 4:
      companyName = "Visa";
      break;
      case 5:
      companyName = "Mastercard";
      break;
      case 6:
      companyName = "Discover";
      break;
      default:
      console.log('Company Not Found');
    }
if(companies.includes(companyName) === false){
  companies.push(companyName);
}
  })
console.log(companies)
}

idInvalidCardCompanies(invalidCards)