使用 lodash 将 Typescript 中的项目分组

Question

我需要按日期对一组对象进行分组：

var meetings =
[
   {date:"2001-01-01 13:00", place:"park"},
   {date:"2001-01-01 14:00", place:"school"},
   {date:"2001-01-02 11:00", place:"house"}
];

所以它变成：

var groupedMeetings = 
[
   {
      day:"2001-01-01", 
      meetings: 
      [
         {date:"2001-01-01 13:00", place:"park"},
         {date:"2001-01-01 14:00", place:"school"}
      ]
   },
   {
      day:"2001-01-02", 
      meetings: 
      [
         {date:"2001-01-02 11:00", place:"house"}
      ]
   }
]

我能够用 _.groupBy 和 _.map 将它们分组

var g = _.groupBy(meetings, function(i){return getDatePart(i.date);});
var groupedMeetings  = _.map(g, function(items,key){return {day:key, meetings:items};});

但是我在使用https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/lodash/lodash.d.ts在 Typescript 中做同样的事情时遇到了问题

首先，我声明了我的课程：

class Meeting
    {
       date: Date,
       place: Meeting[]
    }
class GroupedMeeting
    {
      constructor(private day: Date, private meetings: Meeting[]) {}
    }

现在我不知道要使用 groupBy 的哪个重载？以及如何将其映射到分组项目列表？

var grouped: _.Dictionary<Meeting[]> = _.groupBy(meetings, (i: Meeting) => { return this.getDatePart(i.date); });

var groupedMeetings : GroupedMeeting[] = _.map(grouped, (items: Meeting[], key: Date) => { return new GroupedMeeting (key, items); });

Answer 1

您可以使用该_.groupBy()方法并添加一个回调，该回调返回您需要对其进行分组的值，即日期的年、月、日部分。然后，您可以使用 设置所需的值_.map()。

下面的例子使用 ES6：

var meetings =
[
   {date:"2001-01-01 13:00", place:"park"},
   {date:"2001-01-01 14:00", place:"school"},
   {date:"2001-01-02 11:00", place:"house"}
];

var result = _(meetings)
  .groupBy(meeting => meeting.date.split(' ').shift())
  .map((meetings, day) => ({ day, meetings }))
  .value();

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

<script src="https://cdn.jsdelivr.net/lodash/4.11.2/lodash.min.js"></script>

这是 ES5 版本：

var meetings =
[
   {date:"2001-01-01 13:00", place:"park"},
   {date:"2001-01-01 14:00", place:"school"},
   {date:"2001-01-02 11:00", place:"house"}
];

var result = _(meetings)
  .groupBy(function(meeting) { return meeting.date.split(' ').shift(); })
  .map(function(meetings, day) { return { day: day, meetings: meetings }; })
  .value();

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

<script src="https://cdn.jsdelivr.net/lodash/4.11.2/lodash.min.js"></script>