function quickSort(arr){ if(arr.length <= 1) return arr;//判斷是否有效數組 var cut = Math.floor(arr.length/2);//取中間下標 var left = [],right = []; var num = arr.splice(cut,1)[0];//取基準值 for(var i = 0;i < arr.length;i ++){  if(arr[i] < num){   left.push(arr[i]);//小的放左邊  }else {   right.push(arr[i]);//大的放右邊  } } return quickSort(left).concat(num,quickSort(right));//遞歸}