I am working on a project but I was stumped to see this piece of code if ((array.length - 1 - i) % 2 === 1) I am just curious as to how it works?
const valid1 = [4, 5, 3, 9, 6, 7, 7, 9, 0, 8, 0, 1, 6, 8, 0, 8];
const validateCred = (array) => {
let total = 0;
for (var i = array.length - 1; i >= 0; i--) {
// console.log(array[i])
if ((array.length - 1 - i) % 2 === 1) { /*I would like to know what does this do when put in a if statment array.length - 1 - i */
array[i] *= 2;
// console.log(array[i])
if (array[i] > 9) {
array[i] -= 9;
}
}
total += array[i]
console.log(total)
}
return total % 10 === 0;
};
console.log(validateCred(valid1))array.length - 1: the last index of the arraylastIndex - i: work through the array from back to front (typically)someIndex % 2 === 1: is the index modulus 2 equal to 1 (meaning, is it odd?)But then the loop iterates from the last index to the first index, so the - i just makes it iterate from front to back again. Which seems needlessly complex.
This code is pretty funky...