const arrs = [9, 4, 7, 6, 2, 5, 8, 1, 11];

    2. function quickSort (arr) {
    3.   if (!arr || arr.length === 0) {
    4.     return [];
    5.   }
    6.   let max = arr[0];
    7.   let left = [];
    8.   let right = [];
    9.   for (let i = 1; i < arr.length; i++) {
    10.     if (arr[i] < max) {
    11.       left.push(arr[i])
    12.     } else {
    13.       right.push(arr[i])
    14.     }
    15.   }
    16.   left = quickSort(left);
    17.   right = quickSort(right)
    18.   return [...left, max, ...right];
    19. }console.log(quickSort(arrs))