function sumArray(arr) {
  // Base case: when the array is empty, return 0
  if (arr.length === 0) {
    return 0;
  }
  // Recursive case: add the first element to the sum of the rest of the array
  return arr[0] + sumArray(arr.slice(1));
}

// Test cases
console.log(sumArray([1, 2, 3, 4, 5])); // => 15
console.log(sumArray([10, -2, 33, 47])); // => 88
console.log(sumArray([])); // => 0