main.js

/* Here are some sample arrays of valid, invalid, and unknown credit card numbers, and an array of all of these arrays
// 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,
];

// Functions are below
*/

// Validate credit card numbers
const validateCred = arr => {
   let temp = arr.slice().reverse();
   for (let i = 1; i < temp.length; i += 2) {
      temp[i] *= 2;
      if (temp[i] > 9) {
         temp[i] -= 9;
      }
   }
   const result =
      temp
         .slice()
         .reverse()
         .reduce((a, b) => a + b) %
         10 ===
      0;
   return result;
};

// Return cards that are invalid
const findInvalidCards = arrays => {
   let invalidCards = [];
   for (const arr of arrays) {
      if (!validateCred(arr)) {
         invalidCards.push(arr);
      }
   }
   return invalidCards;
};

// Return list of companies that issued invalid cards
const idInvalidCardCompanies = arrays => {
   let companies = [];
   for (const i of arrays) {
      switch (i[0]) {
         case 3:
            if (!companies.includes('Amex')) {
               companies.push('Amex');
            }
            break;
         case 4:
            if (!companies.includes('Visa')) {
               companies.push('Visa');
            }
            break;
         case 5:
            if (!companies.includes('Mastercard')) {
               companies.push('Mastercard');
            }
            break;
         case 6:
            if (!companies.includes('Discover')) {
               companies.push('Discover');
            }
            break;
         default:
            if (!companies.includes('Company not found')) {
               companies.push('Company not found');
            }
            break;
      }
   }
   return companies;
};

/* Use parseInt to convert credit card numbers to arrays with numbers. */
const convertString = creditCardNumber => {
   let newArr = [];
   for (const i of creditCardNumber) {
      newArr.push(parseInt(i));
   }
   return newArr;
};

// Easier way to validate one card
const validate = creditCardNumber => {
   let newArr = convertString(creditCardNumber);
   return validateCred(newArr);
};

// Tell users if their number is valid or not
const input = document.querySelector('#number');
const output = document.querySelector('#result');
const valid = () => {
   let creditCardNumber = input.value;
   let result = validate(creditCardNumber);
   if (result) {
      output.innerHTML = 'Valid';
      output.style.color = 'green';
   } else {
      output.innerHTML = 'Invalid';
      output.style.color = 'red';
   }
};
// Prevent users from entering invalid characters
const invalidChars = [
  "-",
  "+",
  "e",
];
input.addEventListener("keydown", e => invalidChars.includes(e.key) && e.preventDefault());
// When the user types in an input, run the function
input.addEventListener('keyup', valid);

/*
// Test functions:
console.log(validateCred(valid1)); // Should print true
console.log(validateCred(invalid1)); // Should print false
console.log(findInvalidCards([valid1, valid2, valid3, valid4, valid5])); // Shouldn't print anything
console.log(
  findInvalidCards([invalid1, invalid2, invalid3, invalid4, invalid5])
); // Should print all of the numbers
console.log(findInvalidCards(batch)); // Test what the mystery numbers are
console.log(idInvalidCardCompanies([invalid1])); // Should print['visa']
console.log(idInvalidCardCompanies([invalid2])); // Should print ['mastercard']
console.log(idInvalidCardCompanies(batch)); // Find out which companies have mailed out invalid cards
*/