1. const quickSort = (arr)=>{
    2.     if(arr.length<=1)return arr;
    3.   let pivotIndex = Math.floor(arr.length/2);
    4.   let pivot = arr.splice(pivotIndex,1)[0];
    5.   let left =[];
    6.   let right = [];
    7.   for(let i = 0;i<arr.length;i++){
    8.       if(arr[i]<pivot)left.push(arr[i]);
    9.     else right.push(arr[i]);
    10.   }
    11.   return quickSort(left).concat([pivot],quickSort(right));
    12. }