Credit Card Checker, getting unique strings in array

Hello all,

So far with the help of the forum and google, I managed to complete almost 5 steps of the Credit Card Checker project. However, at step 5 there is a condition that credit card companies should only appear once in an array.
So at the moment, I am not sure how should I implement the indexOf. method in my last function to only receive unique strings in an array. See my code below:

 // 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;
  for (let i = array.length - 1; i >= 0; i--) {
    let currValue = array[i];
    if ((array.length - 1 - i) % 2 === 1) {
      currValue *= 2;
      if (currValue > 9) {
        currValue -= 9;
      }
    }
    sum += currValue;
  }
  return sum % 10 === 0;
}

///function that loops through nested array of credit cards

const findInvalidCards = (cards) => {

  const invalidCards = [];

  for(let i = 0; i <= cards.length - 1; i++) {
    if (validateCred(cards[i]) === false) {
      invalidCards.push(cards[i]);
    }
  }
  return invalidCards;
}

// console.log(findInvalidCards(batch));

const idInvalidCardCompanies = (number) => {

  const creditCompanies = [];

  for(let i = 0; i < number.length; i++ ) {
    let company = number[i];
    if(company[0] === 3) {
      creditCompanies.push('Amex');
    } else if (company[0] === 4) {
      creditCompanies.push('Visa');
    } else if (company[0] === 5) {
      creditCompanies.push('Mastercard');
    } else if (company[0] === 6) {
      creditCompanies.push('Discover');
    } else {
      creditCompanies.push('Company not found');
    }
  }

  for (let j = 0; j < creditCompanies.length; j++) {
    
  }
  return creditCompanies;
}

console.log(idInvalidCardCompanies(findInvalidCards(batch)));

At the moment when my last console.log statement runs I get this result:
[ ‘Visa’,
‘Mastercard’,
‘Amex’,
‘Discover’,
‘Mastercard’,
‘Amex’,
‘Discover’,
‘Visa’ ]

You could use one of these 3 methods. Option nr 2 uses indexOf and combines it with the array filter-method.

Remove duplicates from array

Thank you for your answer. I used the second method, this is how the last function looks now and it seems to work.

const idInvalidCardCompanies = (number) => {

  const creditCompanies = [];

  for(let i = 0; i < number.length; i++ ) {
    let company = number[i];
    if(company[0] === 3) {
      creditCompanies.push('Amex');
    } else if (company[0] === 4) {
      creditCompanies.push('Visa');
    } else if (company[0] === 5) {
      creditCompanies.push('Mastercard');
    } else if (company[0] === 6) {
      creditCompanies.push('Discover');
    } else {
      creditCompanies.push('Company not found');
    }
  }

  for (let j = 0; j < creditCompanies.length; j++) {
    
  }
  let uniqueCompanies = creditCompanies.filter((c, index) => {
    return creditCompanies.indexOf(c) === index;
  });
  return uniqueCompanies;
}

 

console.log(idInvalidCardCompanies(findInvalidCards(batch)));
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