# Credit Card Checker Feedback

This was a fun little project. I wanted to put my solution up here to see if anyone had comments on how I could have done it better.

I am reasonably sure my weird little .reverse() approach might be considered a bit dodge. I wanted the array reversed to run my loops over it but didn’t want to mutate the original array. I was finding if I just made the new array equal to the old one and then reversed my new one… it also reversed the old one. If anyone can explain that, I would appreciate it.

``````// 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];

const validateCred = array => {
const checkArray = array.filter(x => x >= 0);
let doubledSum = 0;
let singleSum = 0;
checkArray.reverse();

for (let i = 1; i < checkArray.length ; i+=2){
//console.log(checkArray[i]);
if ((checkArray[i]*2) > 9){
doubledSum += ((checkArray[i]*2)-9);
} else {
doubledSum += checkArray[i]*2;
}
}
for (let j = 0; j < checkArray.length; j+=2){
singleSum += checkArray[j];

}
const total = (doubledSum + singleSum) % 10;
const valid = (total === 0) ? true : false;
return valid;
}
validateCred(valid1);

const findInvalidCards = nestArr => {
const invalidCards = nestArr.filter(arr => validateCred(arr) === false);
return invalidCards;
}

const idInvalidCardCompanies = nestArr =>{
let companies = [];
for (let i = 0; i < nestArr.length; i++){
let firstDig = nestArr[i][0];
switch (firstDig){
case 3 : companies.push('Amex (American Express)');
break;
case 4 : companies.push('Visa');
break;
case 5 : companies.push('Mastercard');
break;
case 6 : companies.push('Discover');
break;
}
}
return companies.filter((a,b) => companies.indexOf(a) === b);
}

``````

Yes, that’s because an array is a kind of object,
using `=` doesn’t actually create a new object, it just creates a new reference to the same object.

Here’s a link to a previous post on that:
post 858 in credit-card-checker-challenge-project

1 Like

Thanks for clarifying that