Array summation inside a Function

// 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:

function validateCred(arr){
for (let i = 15; i = 0; i–){
if (i % 2 === 0) {
arr[i] = arr[i] *2; {
if (arr[i] > 9){
arr[i] = arr[i] - 9
} else {
arr[i] = arr[i]
}
}
} else {
arr[i] = arr[i]
}
} for (let i = 0; i < arr.length; i++){
let sum = 0;
sum += arr[i];
return sum;
}

  }

console.log(validateCred(valid1));

Okay, the above is my code, and it’s giving me an output of 4, so it’s summing the first element of my array, but not the other elements.

You return sum in the for loop, so it will only ever do the first item.

If I move return right outside the brackets though, I get an error.

Because you declare sum in the for loop.

1 Like

Thank you so much!

I think I should re-read bout scoping!

I know this is a little dated but when I did this project the first time I made code pretty much exactly like yours.
I want to point out that you could reverse the iterator for an array passed as an argument.

instead of:
for(let i = 0; i < arr.length; i++)

then reverse the array and drop the last index.

you can do this instead:
for(let i = arr.length - 1; i >= 0; i--)

then you only have to drop the last index.