JS计数对象匹配一些相同的值

Question

我有一个这样的 json：

 [{
          "semester":"1",
          "classification":"Excellent",
          "schoolYear":"2018"
       },
       {
          "semester":"2",
          "classification":"Intermediate",
          "schoolYear":"2018"
       },
       {
          "semester":"1",
          "classification":"Excellent",
          "schoolYear":"2018"
       },
       {
          "semester":"2",
          "classification":"Good",
          "schoolYear":"2017"
       },
       {
          "semester":"1",
          "classification":"Excellent",
          "schoolYear":"2017"
       },
       {
          "semester":"2",
          "classification":"Good",
          "schoolYear":"2017"
       },
       {
          "semester":"1",
          "classification":"Excellent",
          "schoolYear":"2017"
       },
       {
          "semester":"2",
          "classification":"Fail",
          "schoolYear":"2017"
       },
       {
          "semester":"1",
          "classification":"Good",
          "schoolYear":"2017"
       }]

我希望通过函数按照这种格式输出：

[
  {
    schoolYear: '2018',
    semesters: [
      {
        Excellent: 2,
        Good: 0,
        Intermediate: 0,
        Average: 0,
        Weak: 0,
        Fail: 0
      },
      {
        Excellent: 0,
        Good: 0,
        Intermediate: 1,
        Average: 0,
        Weak: 0,
        Fail: 0
      }
    ]
  },
  {
    schoolYear: '2017',
    semesters: [
      {
        Excellent: 3,
        Good: 1,
        Intermediate: 0,
        Average: 0,
        Weak: 0,
        Fail: 0
      },
      {
        Excellent: 0,
        Good: 2,
        Intermediate: 0,
        Average: 0,
        Weak: 0,
        Fail: 1
      }
    ]
  }
]

如您所见，输出是一个数组，数组中的每个元素都有 2 个属性，schoolYear 是一个字符串，semesters 是一个仅包含 2 个元素的数组，索引 0 处的第一个元素是"semester": "1" 根据输入，索引 1 处的第二个元素是 "semester": "2"，当然。

我要感谢您抽出时间帮助我，您可以在此codeandbox演示here中修改代码，再次感谢您，祝您有美好的一天

Answer 1

这是一个工作示例：

var obj = [
    {
        semester: "1",
        classification: "Excellent",
        schoolYear: "2018"
    },
    {
        semester: "2",
        classification: "Intermediate",
        schoolYear: "2018"
    },
    {
        semester: "1",
        classification: "Excellent",
        schoolYear: "2018"
    },
    {
        semester: "2",
        classification: "Good",
        schoolYear: "2017"
    },
    {
        semester: "1",
        classification: "Excellent",
        schoolYear: "2017"
    },
    {
        semester: "2",
        classification: "Good",
        schoolYear: "2017"
    },
    {
        semester: "1",
        classification: "Excellent",
        schoolYear: "2017"
    },
    {
        semester: "2",
        classification: "Fail",
        schoolYear: "2017"
    },
    {
        semester: "1",
        classification: "Good",
        schoolYear: "2017"
    }
];
const formatArray = (oldArray) => {

    const newArray = [];
    oldArray.forEach((oldEntry) => {
        let newObjIndex = newArray.findIndex((e) => e.schoolYear === oldEntry.schoolYear);
        if (newObjIndex === -1) {
            newArray.push({
                schoolYear: oldEntry.schoolYear
            });
            newObjIndex = newArray.length - 1;
        }
        if (!newArray[newObjIndex].semester) {
            newArray[newObjIndex].semester = [];
        }
        if (!newArray[newObjIndex].semester[oldEntry.semester]) {
            newArray[newObjIndex].semester[oldEntry.semester] = {};
        }
        newArray[newObjIndex].semester[oldEntry.semester][oldEntry.classification] = newArray[newObjIndex].semester[oldEntry.semester][oldEntry.classification]
            ? newArray[newObjIndex].semester[oldEntry.semester][oldEntry.classification] + 1
            : 1;
    });
    return newArray;
};
console.log(formatArray(obj));