I am confused because I don’t understand why do we need to pass array as argument here, when it works same if we only pass n, which makes it simpler for me to understand.

```
const arr = [2,3,4,5]
function sum(n) {
if(n <= 0) {
return 0;
} else {
return sum(n - 1) + arr[n - 1];
}
}
```