js 快排

原理：

每次排序都设置一个low和high ，当前项为x,首先从low开始向后搜索找到一个大于x的记录，然后交换，再从high向前搜索找到小于x的记录，然后交换。一直重复着两步，知道low=high位置，再分别对两个子序列排序，直到每个子序列只含一个记录为止

性能：

代码如下：

let arr = [1, 9, 2, 10, 3, 11, 4, 12, 5, 13, 6, 14, 7, 15, 8, 16];
        function quickSort(arr, low, high) {
            if (low >= high) {
                return;
            }
            let current = arr[low];
            //存储初始的low和high
            let initLow = low;
            let initHigh = high;
            while (low < high) {
                //找到比当前项小的
                while (low < high && arr[high] >= current) {
                    high--;
                }
                if (low < high) {
                    //交换
                    arr[low] = arr[high]
                    low++;
                }
                //找到比当前项大的
                while (low < high && arr[low] <= current) {
                    low++;
                }
                if (low < high) {
                    //交换
                    arr[high] = arr[low]
                    high--;
                }
            }
            arr[low] = current;
            quickSort(arr, initLow, high - 1)
            quickSort(arr, high + 1, initHigh)
        }