这个树形结构怎么转换？

Question

let arr = [
                                        {day:2021-1-1,day1:'全天',time:00:00,name:123},
                                        {day:2021-1-1,day1:'全天',time:00:00,name:456},
                                        {day:2021-1-1,day1:'非全天',time:10:00,name:789},
                                        {day:2021-1-2,day1:'非全天',time:10:00,name:777},
                                        {day:2021-1-2,day1:'非全天',time:10:00,name:888},
                                    ]

运行结果

let List=[
                                        {
                                            day:2021-1-1,
                                           children:[
                                               {
                                                    time:00:00,
                                                    children:[
                                                        {day:2021-1-1,day1:'全天',time:00:00,name:123},
                                                        {day:2021-1-1,day1:'全天',time:00:00,name:456},
                                                    ],
                                                },
                                                {
                                                    time:10:00,
                                                    children:[
                                                        {day:2021-1-1,day1:'非全天',time:10:00,name:789},
                                                    ]
                                                }
                                           ],
                                        },
                                        {
                                            day:2021-1-2,
                                            children:[
                                                {
                                                    time:10:00,
                                                    children:[
                                                        {day:2021-1-2,day1:'非全天',time:10:00,name:777},
                                                        {day:2021-1-2,day1:'非全天',time:10:00,name:888},
                                                    ],
                                                }
                                            ]
                                        }
                                    ]
```javascript

```

Answer 1

let List = [];

for (let i = 0; i < arr.length; i++) {
  let item = arr[i];
  let dayIndex = -1;
  for (let j = 0; j < List.length; j++) {
    if (List[j].day === item.day) {
      dayIndex = j;
      break;
    }
  }
  if (dayIndex === -1) {
    List.push({
      day: item.day,
      children: []
    });
    dayIndex = List.length - 1;
  }
  let timeIndex = -1;
  for (let j = 0; j < List[dayIndex].children.length; j++) {
    if (List[dayIndex].children[j].time === item.time) {
      timeIndex = j;
      break;
    }
  }
  if (timeIndex === -1) {
    List[dayIndex].children.push({
      time: item.time,
      children: []
    });
    timeIndex = List[dayIndex].children.length - 1;
  }
  List[dayIndex].children[timeIndex].children.push(item);
}