Credit Card Checker - idInvalidCardCompanies: array.filter

I’m stuck on the Credit Card Checker project (JavaScript) in the Back End Engineer path. Specifically, I’m on the final step of the idInvalidCardCompanies function, and I just cannot get the array.filter method to work. After hours of banging my head against a wall, I switched directions and added code to check for the credit card company in the array before adding it instead of filtering for duplicates after the fact. I was able to complete the project with a functioning credit card checker by doing this, but I know it’s possible to filter an array for duplicates, and I’m extremely frustrated that I can’t get it to work. Can anyone see what I’m missing in the idInvalidCardCompanies function below? Thanks!

// 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 = ccNum => {
    let luhnCCNum = ccNum.map(num => {return num});
    for (i = luhnCCNum.length - 2; i >= 0; i = i - 2) {
        luhnCCNum[i] = luhnCCNum[i] * 2;
        if (luhnCCNum[i] > 9) {
            luhnCCNum[i] = luhnCCNum[i] - 9;
        }
    }
    let ccSum = 0;
    for (i = 0; i < luhnCCNum.length; i++) {
        ccSum = ccSum + luhnCCNum[i];
    }
    const luhnMod = ccSum % 10;
    return luhnMod === 0;
}

const findInvalidCards = ccList => {
    let invalidCards = [];
    ccList.forEach(ccNum => {
        if (validateCred(ccNum) === false) {
            invalidCards.push(ccNum);
        }
    })
    return invalidCards;
}

const badBatch = findInvalidCards(batch);

const idInvalidCardCompanies = invalidCardList => {
    let invalidCardCompanies = [];
    invalidCardList.forEach(card => {
        switch (card[0]) {
            case 3 :
                invalidCardCompanies.push('Amex');
                break;
            case 4:
                invalidCardCompanies.push('Visa');
                break;
            case 5:
                invalidCardCompanies.push('Mastercard');
                break;
            case 6:
                invalidCardCompanies.push('Discover');
                break;
            default:
                invalidCardCompanies.push('Company not found');
        }
    })
    let uniqueInvalidCardCompanies = invalidCardCompanies.filter((item, pos) => {invalidCardCompanies.indexOf(item) == pos});
    return invalidCardCompanies;
}

console.log(idInvalidCardCompanies(badBatch));

You have to take out the { } in the function you are using to filter, so you could use:
(item, pos) => invalidCardCompanies.indexOf(item) == pos
or you have to include a return there:
(item, pos) => { return invalidCardCompanies.indexOf(item) == pos}

I also think that last return for the idInvalidCardCompanies function should be different:
return invalidCardCompanies;
should be:
return uniqueInvalidCardCompanies;

let arr = ['a', 'b', 'a', 'c', 'b']; let arr2 = arr.filter((item, pos) => arr.indexOf(item) == pos); console.log(arr2);
1 Like

Thank you!!! I tried that and it worked.