无法得到想要的结果数组

Question

我目前正在学习 lodash 和 moment.js，我正在使用一些虚拟数据。包含 1000 名医生列表的虚拟数据。我已经开始使用 Array.prototype.map() 和 Array.prototype.filter() 并将很快将它们转换为 lodash。

数据

var doctors = [
  {
    "id": 0,
    "dateOfEmployment": "2012-12-27",
    "dateOfTermination": "2015-01-13",
    "dateOfBirth": "1978-06-06",
    "gender": "Male"
  },
  {
    "id": 1,
    "dateOfEmployment": "2016-02-08",
    "dateOfTermination": null,
    "dateOfBirth": "1984-04-21",
    "gender": "Female"
  },
  {
    "id": 2,
    "dateOfEmployment": "2010-11-30",
    "dateOfTermination": "2015-09-03",
    "dateOfBirth": "1975-09-24",
    "gender": "Male"
  },
  {
    "id": 3,
    "dateOfEmployment": "2012-06-17",
    "dateOfTermination": null,
    "dateOfBirth": "1980-08-31",
    "gender": "Female"
  },..];

我想获得过去 2 年的数组结果：

[{ date: '2015-04', count: 22 }, 
 { date: '2015-05', count: 25 },
 ...]

最初我尝试过这个：

    doctors = doctors.filter(function(doctor){
             return moment(doctor.dateOfEmployment).isBetween('2014-04', '2016-04');   
          }).map(function(doctor){
              return  {
            dates: moment(doctor.dateOfEmployment).format('YYYY-MM'),
            count: new Date(doctor.dateOfEmployment) - new Date(doctor.dateOfEmployment) + 1 };
      }););


console.log(doctors);

我很困惑。我是否应该首先使用 id、dateOfEmployment、dateOfTermination 创建一个新的医生数组，然后记下这两个日期。然后过滤新的日期数组，条件是时刻为年份之间，然后映射/减少。

我确实想到了蛮力方法，我会在每个医生身上循环 24 次，并根据条件增加一个计数器，即 if doctorsEmployment 日期和 doctorsTermination 日期为 null 或等于临时日期。临时日期从 '2014-04' 到 '2016-04' 并最终将其推送到数组结果对象。

我是否以错误的方式处理这个问题？

任何帮助将不胜感激！

Answer 1

不是 lodash 或 moment.js，但这里是如何在纯 JS 中做到这一点：

// Sample data
var doctors = [
  {
    "id": 0,
    "dateOfEmployment": "2012-12-27",
    "dateOfTermination": "2015-01-13",
    "dateOfBirth": "1978-06-06",
    "gender": "Male"
  },
  {
    "id": 1,
    "dateOfEmployment": "2016-02-08",
    "dateOfTermination": null,
    "dateOfBirth": "1984-04-21",
    "gender": "Female"
  },
  {
    "id": 2,
    "dateOfEmployment": "2016-02-29",
    "dateOfTermination": "2015-09-03",
    "dateOfBirth": "1975-09-24",
    "gender": "Male"
  },
  {
    "id": 3,
    "dateOfEmployment": "2015-06-17",
    "dateOfTermination": null,
    "dateOfBirth": "1980-08-31",
    "gender": "Female"
  }];
 
// Parse ISO date string (e.g. 2016-04-01) as local
function parseISODate(s) {
  var b = s.split(/\D/);
  return new Date(b[0], b[1]? b[1] - 1 : 0, b[2] || 1);
}

var startDate = parseISODate('2014-04'),
    endDate   = parseISODate('2016-04');

// Creates an object with months and counts
var resultObj = doctors.reduce(function(acc, cur) {
  var d = parseISODate(cur.dateOfEmployment);
  if (d >= startDate && d <= endDate) {
    var month = d.toISOString().slice(0,7);
    acc[month] = (acc[month] || 0) + 1;
  }
  return acc;
}, {});

// Creates an array with required objects from result object
var resultArr = Object.keys(resultObj).map(function(key) {
  return {date: key, count: resultObj[key]};
})
 
document.write(
  JSON.stringify(resultObj) + '<br>' + // {"2016-02":2,"2015-06":1}
  JSON.stringify(resultArr)  // [{"date":"2016-02","count":2},{"date":"2015-06","count":1}]
);

这假设您只需要计数大于零的月份。它遍历原始数据一次，然后遍历结果对象一次，尽管我看不出数组是比创建它的对象更理想的格式。

请注意，我将源数据编辑为在 2016 年 2 月有两个 dateOfEmployment 日期。

Answer 2

如何使用 lodash 的 reduce...像这样：

var doctors = [{
  "id": 0,
  "dateOfEmployment": "2014-12-27",
  "dateOfTermination": "2015-01-13",
  "dateOfBirth": "1978-06-06",
  "gender": "Male"
}, {
  "id": 1,
  "dateOfEmployment": "2016-02-08",
  "dateOfTermination": null,
  "dateOfBirth": "1984-04-21",
  "gender": "Female"
}, {
  "id": 2,
  "dateOfEmployment": "2015-11-30",
  "dateOfTermination": "2015-09-03",
  "dateOfBirth": "1975-09-24",
  "gender": "Male"
}, {
  "id": 3,
  "dateOfEmployment": "2012-06-17",
  "dateOfTermination": null,
  "dateOfBirth": "1980-08-31",
  "gender": "Female"
}];

doctors = _.reduce(doctors, function(memo, doctor) {
  if (moment(doctor.dateOfEmployment).isBetween('2014-04', '2016-04')) {
    memo.push({
      dates: moment(doctor.dateOfEmployment).format('YYYY-MM'),
      count: new Date(doctor.dateOfEmployment) - new Date(doctor.dateOfEmployment) + 1
    });
  }
  return memo;
}, []);
console.log(doctors);

工作fiddle