Help with Credit Card Checker Assignment

Hello, I am not sure if anyone is stuck with this assignment. I am trying to do the ValidateCred part with the following code, but keep getting ‘false’ returned. If someone can give me some help, really appreciate it. Thank you!!

function validateCred(numArray) {
let total;
let currValue;
for (let i = numArray.length - 1; i >= 0; i–) {
if (i % 2 != 0) {
currValue = numArray[numArray.length - 1 - i] * 2;
if (currValue >= 10) {
currValue = currValue - 9;
}
}
else if (i % 2 === 0) {
currValue = numArray[numArray.length - 1 - i];
}
}
total += currValue;
if (total % 10 === 0) {
return true;
} else {
return false;
}
}

console.log(validateCred(valid1));