**Tell us what’s happening:**

I don’t understand why decrement doesn’t work: (n–) doesn’t pass test, (n-1) does.

E.g., this works:

```
function sum(arr, n) {
// Only change code below this line
if (n <= 0) return 0;
else return sum(arr, n-1) + arr[n-1];
// Only change code above this line
}
```

This doesn’t:

```
function sum(arr, n) {
// Only change code below this line
if (n <= 0) return 0;
else return sum(arr, n--) + arr[n--];
// Only change code above this line
}
```

**Your code so far**

```
function sum(arr, n) {
// Only change code below this line
if (n <= 0) return 0;
else return sum(arr, n--) + arr[n--];
// Only change code above this line
}
```

**Your browser information:**

User Agent is: `Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:84.0) Gecko/20100101 Firefox/84.0`

.

**Challenge:** Replace Loops using Recursion

**Link to the challenge:**