数组两个参数之间交换位置 使用splice方法实现

 //上移
    topStudent(index) {
      this.studentData.splice(
        index,
        1,
        ...this.studentData.splice(index - 1, 1, this.studentData[index])
      );
    },
    //下移
    bottomStudent(index) {
      this.studentData.splice(
        index + 1,
        1,
        ...this.studentData.splice(index, 1, this.studentData[index + 1])
      );
    },