如何将 result 转换为 newResult 的数据结构, 根据 groupQuestionId的相同, 来添加index, 作为序号
```javascript
let result = [
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15615},
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15615},
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15615},
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15616},
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15617}
]
let newResult = [
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15615, index: '1-1'},
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15615, index: '1-2'},
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15615, index: '1-3'},
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15616, index: '2'},
{avgScore: null,createTime: "2022-05-20 13:59:05",createUserId: 61622,groupQuestionId: 15617, index: '3'}
]
```