codecademy project

credit_card_checker.js

// All valid credit card numbers
const valid1 = [4, 5, 3, 9, 6, 8, 9, 8, 8, 7, 7, 0, 5, 7, 9, 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];




// Luhn algorithm used to verify if card number is valid:
 const validateCred = cardNumber => {
  let toSum = [];
// drop last digit:
 toSum.push(cardNumber[cardNumber.length-1])
 cardNumber.pop();
//  reverse digits:
 cardNumber.reverse()
//  multiple every other digit by 2, subtract 9 to numbers over 9:
  for (digitIndex = 0; digitIndex < cardNumber.length; digitIndex++) {
    if (digitIndex % 2 == 0){
      let digitToChange = cardNumber[digitIndex] * 2;
      if (digitToChange > 9) {
        digitToChange -= 9;
      } 
      toSum.push(digitToChange);
    } else {
      toSum.push(cardNumber[digitIndex])
    }
  }
// Add all numbers; sum modulo 10 is 0 -> valid, otherwise, it’s invalid:
 let sum = toSum.reduce((a, b) => a + b);
 return sum % 10 === 0 ? true : false;
}

// check through the nested array for which numbers are invalid, and return another array with first digits:
const findInvalidCards = (cardNumbers) => {
  let invalid = [];
   cardNumbers.forEach(cardNumber => {
     if (validateCred(cardNumber) === false) {
       invalid.push(cardNumber[cardNumber.length-1]);
     }
   })
   return invalid
}

// identify the credit card companies that have possibly issued faulty numbers:
const idInvalidCardCompanies = (cardNumbers) => {
  let invalid = findInvalidCards(cardNumbers);
  let comapnies = [];
  for (i = 0; i < invalid.length; i++){
    if (i === 3 && !comapnies.includes('Amex (American Express)'))  {
      comapnies.push('Amex (American Express)');
    } else if (i === 4 && !comapnies.includes('Visa')) {
      comapnies.push('Visa');
    } else if (i === 5 && !comapnies.includes('Mastercard')) {
      comapnies.push('Mastercard');
    } else if (i === 6 && !comapnies.includes('Discover')) {
      comapnies.push('Discover');
    } else {
      'Company not found'
    }
  }
  return comapnies;
}

// function that accepts a string and converts it into an array of numbers, and then checks if number is valid: 
 const convertAndCheck = num => {
   let convertedNumb = String(num).split('').map(Number);
   return validateCred(convertedNumb);
 }
 




console.log(convertAndCheck(379064703661354)) // output: true
console.log(validateCred(mystery4)) // output: false
console.log(idInvalidCardCompanies(batch)) // output: [ 'Amex (American Express)', 'Visa', 'Mastercard', 'Discover' ]