Credit Card Checker Complete (finally)

This project was by the most challenging project I have done yet.

I am looking on any feedback people may have on my code as I am extremely new to Javascript/Programming.

// 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:
//Copy, remove last digit and reverse valid1 CC number
const validateCred = (valid1) => {
  let valid1Test = [];
  valid1Test = valid1.slice();
  valid1Test.pop();
  valid1Test.reverse();

  //Double every second number and -9 if result is > 9
  for (let i = 0; i < valid1Test.length; i += 2) {
    valid1Test[i] *= 2;
  }
  for (let i = 0; i < valid1Test.length; i++) {
    if (valid1Test[i] > 9) {
      valid1Test[i] -= 9;
    }
  }

  //Sum the valid1Test array and add last digit of valid1 then check validity using Luhn
  let sumTotal = valid1Test.reduce((a, b) => a + b, 0);

  let num1 = sumTotal + valid1.pop();
  if (num1 % 10 === 0) {
    return true;
  } else {
    return false;
  }
};
//Fucntion that utilises validateCred function to check through all of the cards in the batch array
let invalidCards = [];
const findInvalidCards = (batch) => {
  let batchIndex = 0;
  for (let batchIndex = 0; batchIndex < batch.length; batchIndex++)
    if (validateCred(batch[batchIndex]) === false) {
      invalidCards.push(batch[batchIndex]);
    }
  return invalidCards;
};
// Test - Should print array of Invalid Cards
console.log(findInvalidCards(batch));

//function that ids the company associate with invalid cards in invalidCard array
function idInvalidCardCompanies(invalidCards) {
  const companies = [];
  for (let i = 0; i < invalidCards.length; i++) {
    switch (invalidCards[i][0]) {
      case 3:
        if (companies.indexOf("Amex") === -1) {
          companies.push("Amex");
        }
        break;
      case 4:
        if (companies.indexOf("Visa") === -1) {
          companies.push("Visa");
        }
        break;
      case 5:
        if (companies.indexOf("Mastercard") === -1) {
          companies.push("Mastercard");
        }
        break;
      case 6:
        if (companies.indexOf("Discover") === -1) {
          companies.push("Discover");
        }
        break;
      default:
        console.log("Company not found");
    }
  }
  return companies;
}
// Should print companies that have invalid cards
console.log(idInvalidCardCompanies(invalidCards));

I am still a little confused about the following line of code
if (companies.indexOf("Amex") === -1) { companies.push("Amex");
what exactly is this checking - specifically the ===-1?

Cheers,
Jordan

1 Like

Hi there!

Your answer lies in the documentation, specifically:

The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.

Your comparison, therefore, is testing for the absence of a specific item in that array. :slight_smile:

Edit: There are some places where you could streamline your code, but overall I’d say it’s not a bad effort. :+1:

1 Like