QuickSort [JavaScript]

quicksort.js

function swap(arr, firstIndex, secondIndex) {
  const buf = arr[firstIndex];
  arr[firstIndex] = arr[secondIndex];
  arr[secondIndex] = buf;
}

function partition(arr, left, right) {
  let pivot = arr[Math.floor((right + left) / 2)],
      i = left,
      j = right;
  
  while (i <= j) {
    
    while (arr[i] < pivot) {
      i++;
    }
    
    while (arr[j] > pivot) {
      j--;
    }
    
    if (i <= j) {
      swap(arr, i, j);
      i++;
      j--;
    }
  }
  
  return i;
  
}

function quickSort(arr, left = 0, right = arr.length - 1) {
  let i;
  
  if (arr.length > 1) {
    i = partition(arr, left, right);
    
    if (left < i - 1) {
      quickSort(arr, left, i - 1);
    }
    
    if (i < right) {
      quickSort(arr, i, right);
    }
  }
  
  return arr;
}

console.log(quickSort([4, 1, 10, 0, 15]))