js写快排

        function quickSort(arr, startindex) {
            if (arr.length <= 1) {
                return arr;
            }
            const right = [];
            const left = [];
            const startNum = arr.splice(startindex, 1)[0];
            for (let i = 0; i < arr.length; i++) {
                if (arr[i] < startNum) {
                    left.push(arr[i]);
                }
                else {
                    right.push(arr[i]);
                }
            }

            return [...quickSort(left), startNum, ...quickSort(right)];
        }