如何根据其他属性对对象的某些属性进行分组答案

【问题标题】：How to group some properties of objects based on other property如何根据其他属性对对象的某些属性进行分组
【发布时间】：2020-12-05 05:21:28
【问题描述】：

我有一个来自数据库的 json 响应，如下所示：

"gradings": [
    {
        "gradingId": 1,
        "enrollment": {
            "enrollmentId": 1,
            "rollNo": "1PC-1"
        },
        "grade": {
            "name": "B-"
        }
    },
    {
        "gradingId": 2,
        "enrollment": {
            "enrollmentId": 1,
            "rollNo": "1PC-1"
        },
        "grade": {
            "name": "A+"
        }
    },
    {
        "gradingId": 3,
        "enrollment": {
            "enrollmentId": 2,
            "rollNo": "1PC-2"
        },
        "grade": {
            "name": "C-"
        }
    },
    {
        "gradingId": 4,
        "enrollment": {
            "enrollmentId": 2,
            "rollNo": "1PC-2"
        },
        "grade": {
            "name": "C-"
        }
    }
]

我需要将上面的对象转换成下面的结构：

我想将 grades 分组到一个数组中以获得相同的 enrollmentId。

"gradings": [
    {
      enrollmentId: 1,
      rollNo: "1PC-1",
      grades: [B-, A+]
    },
    {
      enrollmentId: 2,
      rollNo: "1PC-2",
      grades: [C-, C-]
    }
  ]

我没有看到任何合适的解决方案来满足我的要求，我也搜索了 lodash。

我该怎么办？我怎样才能做到这一点？谢谢。

【问题讨论】：

标签： javascript object lodash

【解决方案1】：

您应该按enrollmentId 对成绩进行分组，有一个存储唯一注册的数组，map 通过该数组，然后补充该注册的成绩

以下解决方案（在 vanilla js 中）可以帮助您

const { gradings } = {
  gradings: [
    {
      gradingId: 1,
      enrollment: {
        enrollmentId: 1,
        rollNo: "1PC-1",
      },
      grade: {
        name: "B-",
      },
    },
    {
      gradingId: 2,
      enrollment: {
        enrollmentId: 1,
        rollNo: "1PC-1",
      },
      grade: {
        name: "A+",
      },
    },
    {
      gradingId: 3,
      enrollment: {
        enrollmentId: 2,
        rollNo: "1PC-2",
      },
      grade: {
        name: "C-",
      },
    },
    {
      gradingId: 4,
      enrollment: {
        enrollmentId: 2,
        rollNo: "1PC-2",
      },
      grade: {
        name: "C-",
      },
    },
  ],
}

const enrollmentById = {}
const gradesByEnrollmentId = {}

gradings.forEach((grading) => {
  if (!gradesByEnrollmentId[grading.enrollment.enrollmentId]) {
    gradesByEnrollmentId[grading.enrollment.enrollmentId] = [grading.grade.name]
  } else {
    gradesByEnrollmentId[grading.enrollment.enrollmentId].push(grading.grade.name)
  }

  if (!enrollmentById[grading.enrollment.enrollmentId]) {
    enrollmentById[grading.enrollment.enrollmentId] = { ...grading.enrollment }
  }
})

const res = {
  gradings: Object.values(enrollmentById).map((enrollment) => ({
    ...enrollment,
    grades: gradesByEnrollmentId[enrollment.enrollmentId],
  })),
}

console.log(res)

【讨论】：