js快速排序

var quickSort = function (arr) {
            if (arr.length <= 1) {
                return arr;
            }
            var pivotIndex = Math.floor(arr.length / 2);
            var pivot = arr.splice(pivotIndex, 1)[0];
            var left = [];
            var right = [];
            for (var i = 0; i < arr.length; i++) {
                if (arr[i] < pivot) {
                    left.push(arr[i]);
                } else {
                    right.push(arr[i]);
                }
            }
            return quickSort(left).concat([pivot], quickSort(right));
        };