Challenge Project: Credit Card Checker

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 = (array) => {
  let sum = 0;
  if (array.length % 2 == 0) {
    for (let i = array.length - 2; i >= 0; i--) {
      if (i % 2 == 0) {
        let num = array[i] * 2;
        if (num > 9) {
          let newNum = num - 9;
          sum += newNum;
        } else {
          sum += num;
        }
      } else {
        sum += array[i];
      }
    }
  } else {
    for (let i = array.length - 2; i >= 0; i--) {
      if (i % 2 != 0) {
        let num = array[i] * 2;
        if (num > 9) {
          let newNum = num - 9;
          sum += newNum;
        } else {
          sum += num;
        }
      } else {
        sum += array[i];
      }
    }
  }
  sum = sum + array[array.length - 1];
  if (sum % 10 == 0) {
    return true;
  } else {
    return false;
  }
};
// Test functions:
console.log(validateCred(valid1)); // Should print true
console.log(validateCred(invalid1)); // Should print false

const findInvalidCards = (nestedArray) => {
  let invalidCards = [];
  for (let array of nestedArray) {
    if (!validateCred(array)) {
      invalidCards.push(array);
    }
  }
  return invalidCards;
};
// Test function
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

const idInvalidCardCompanies = (invalidCards) => {
  const companies = [];
  for (let cardNumber in invalidCards) {
    let company = "";
    switch (invalidCards[cardNumber][0]) {
      case 3:
        company = "Amex (American Express)";
        break;
      case 4:
        company = "Visa";
        break;
      case 5:
        company = "Mastercard";
        break;
      case 6:
        company = "Discover";
        break;
      default:
        console.log("Company not found");
    }
    if (!companies.includes(company)) {
      companies.push(company);
    }
  }
  return companies;
};
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