replacing using recursion javascript code example

Example: replace loops using recursion

//Write a recursive function, sum(arr, n), that returns the sum of the first n elements of an array arr.
  /* 1) sum([1], 0) should equal 0.
     2) sum([2, 3, 4], 1) should equal 2.
     3) sum([2, 3, 4, 5], 3) should equal 9. */
     
function sum(arr, n) {
    if(n <= 0) {
      return 0;
    } else {
      return sum(arr, n - 1) + arr[n - 1];
    }
  }