如何从嵌套数组中获取不同的数组值[关闭]

Question

我想从嵌套数组对象中获取不同的studentId和classNo。

Const arr = [
{
    "studentId": 70,
    "data": [      
      {
        "studentId": 70,
        "teacher": "Syam",
        "classNo": 100,
      },      
      {
        "studentId": 70,
        "teacher": "Mathew",
        "classNo": 101,
      },
    ]
  },
  {
    "studentId": 69,
    "data": [
      {
        "studentId": 69,
        "teacher": "Sam",
        "classNo": 102,
      },
      {
        "studentId": 69,
        "teacher": "Chris",
        "classNo": 101,
      },  
    ]
  }
]

我想根据studentId填充唯一的classNo数组的结果...

expecting like this..
[
  70: [100, 101],
  60: [102, 101]
]

OR

[
  {studentId: 70, classNo: [100, 101]},
  {studentId: 60, classNo: [102, 101]}
]

I have tried below code and not getting the required result.
arr.map((dt) => dt.data.map((item)=> item.studentId).filter((item, i, arr) => arr.indexOf(item) === i))

请任何人帮助我解决这个问题。

Answer 1

用reduce方法解决

 arr.reduce((a,i)=>{
let t = i.data.map(x=>x.classNo).filter(x=>x!=='');
if(a[i.studentId]){
    a[i.studentId] = [...t,...a[i.studentId]]
} else {
     a[i.studentId] = [...t]
}
a[i.studentId] = [...new Set(a[i.studentId])]
return a;

},{})