qsort.js

function qsort(arr) {
  partSort(arr, 0, arr.length - 1);
}
function partSort(arr, start, end) {
  if (start >= end) {
    return;
  }
  const p = arr[end];
  let left = start;
  let right = end;
  while (left < right) {
    while (arr[left] <= p && left < right) {
      left++;
    }
    while (arr[right] >= p && left < right) {
      right--;
    }
    swap(arr, left, right);
  }
  swap(arr, left, end);
  partSort(arr, start, left - 1);
  partSort(arr, left + 1, end);
}
function swap(arr, left, right) {
  const tmp = arr[left];
  arr[left] = arr[right];
  arr[right] = tmp;
}