[Algorithms] Quicksort algorithm using TypeScript

export function quickSort(array) {
  array = [...array];
  partition(array, 0, array.length);
  return array;
}

function partition(array, start, end) {
  const length = end - start;
  if (length <= 1) return;

  // select the pivot
  const pivotIndex = start + Math.floor(Math.random() * length);
  // move the pivot to the beginning of the array
  [array[start], array[pivotIndex]] = [array[pivotIndex], array[start]];
  // get the pivot value
  const pivot = array[start];
  // get the pivot index
  let pivotRank = start;
  // loop thought the array, swap every number each is smaller
  // than the pivor
  for (let index = start + 1; index < end; index++) {
    if (array[index] < pivot) {
      // increase the rank poisition first
      pivotRank++;
      // swap the current number and rand poisition
      [array[index], array[pivotRank]] = [array[pivotRank], array[index]];
    }
  }
  // move the pivot to the pivotRank position
  if (pivotRank !== start) {
    [array[start], array[pivotRank]] = [array[pivotRank], array[start]];
  }

  partition(array, start, pivotRank);
  partition(array, pivotRank + 1, end);
}

const test = [5, 1, 8, 7, 4, 3, 6, 9];
const res = quickSort(test);

document.write(res);