function quickSort(arr) { if (arr.length <= 1) { return arr; } let pivotIndex; if (arr.length % 2 ===0) { pivotIndex = Math.floor(arr.length / 2 - 1); }else { pivotIndex = Math.floor(arr.length / 2); } let pivot = arr[pivotIndex]; let left = []; let right = []; for (let i = 0; i < pivotIndex; i++) { if (arr[i] < pivot) { left.push(arr[i]); } else { right.push(arr[i]); } } for (let j = pivotIndex + 1; j < arr.length; j++) { if (arr[j] < pivot) { left.push(arr[j]); }else { right.push(arr[j]); } } return quickSort(left).concat(pivot,quickSort(right)); } const arr = [90,3,2,1,5,8,9,20,40,21,3]; console.log(quickSort(arr));