# Question about credit card checker

Hi, I’ve managed to do #3 on credit card checker - hooray, didn’t think I could. But I have a question. In order to get it to do something to every other number working right to left, I’ve used ([i] % 2 === 0) but I guess this would only work if the number were always 16 digits long, for an odd-length number it would need to start with a modulo that isn’t equal to 0. How should I could I write it differently so that it works whatever length the number array is?

``````const valid5 = [4, 5, 3, 9, 4, 0, 4, 9, 6, 7, 8, 6, 9, 6, 6, 6];
const invalid1 = [4, 5, 3, 2, 7, 7, 8, 7, 7, 1, 0, 9, 1, 7, 9, 5];

const validateCred = (array) => {
let newArray = [];
let lastDigit = array.pop()

for(let i = array.length-1; i>=0; i--){  if([i] % 2 === 0) {
if((array[i]*2) > 9) {newArray.push(array[i]*2-9)} else {
newArray.push(array[i]*2)} } else
newArray.push(array[i]);}
const reducer = (accumulator, currentValue) => accumulator + currentValue;
if (answer % 10 === 0) {return `Credit Card number is valid`} else {return `Credit Card number is invalid`};
}

console.log(validateCred([6, 0, 1, 1, 1, 2, 7, 9, 6, 1, 7, 7, 7, 9, 3, 5]));
``````

Hey nicolahearn

what does this conditional do?

``````([i] % 2 === 0)
``````

I think I’m going to delete this. When I got to step 4 I found out that my code didn’t work properly All because I needed to answer the question I already asked about the card numbers being different lengths. Have figured it out now!

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