Credit Card Checker: Help

Hi,

I’m currently working on the Credit Card Checker challenge project. I managed to finish the first part of the challenge (until task 3) with the code returning the expected answers.

// 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 = arr => { const arrO = arr let lastDigit = arr.pop(); let numResult = 0 + lastDigit; for (let i = 0; i < arr.length; i++){ arr.reverse(); if (i%2 === 0){ arr[i] *= 2; if (arr[i] > 9){ arr[i] -= 9; } } numResult += arr[i] } if (numResult%10 === 0){ return true } else { return false } } //============================// const findInvalidCards = arr1 =>{ for (let j = 0; j < arr1.length; j++){ if (validateCred(arr1[j]) === false){ console.log(arr1[j]) } } } findInvalidCards(batch)

The `validateCred` function is working as needed on its own.

Once I use the function inside the `findInvalidCards` function, it prints out the credit card number after running the loop (inside the `validateCred`) instead of just running the function and returning the original array inputed.

Also, for some reason, the `findInvalidCards` prints the value of `valid5` although when tested it returns true.

How can I fix that? I’ve been stuck for a while trying to figure it out

``````  const arrO = arr
does not make a copy of the array. What you do afterwards (like `.pop()` changes the original array also. Even if you used the newly created variable. Make a copy with the spread syntax (`[...arr]` or the `.slice()` method.
This: `arr.reverse();` only needs to be done once. And you need that in order to the the forwards for loop. So it doesn’t belong inside the for loop.