その月が何日あるのかをさっと計算する

https://shunshun94.github.io/shared/other/io/github/shunshun94/util/timeutil.jsこんなのを書いた。

// 2019年の2月が何日あるのかを計算している
console.log(1, io.github.shunshun94.util.Time.getMonthDays('2019/2') );
console.log(2, io.github.shunshun94.util.Time.getMonthDays('2019/02') );
console.log(3, io.github.shunshun94.util.Time.getMonthDays('2019-2') );
console.log(4, io.github.shunshun94.util.Time.getMonthDays('2019-02') );
console.log(5, io.github.shunshun94.util.Time.getMonthDays(2019, 2) );
console.log(6, io.github.shunshun94.util.Time.getMonthDays('2019', '2') );
console.log(7, io.github.shunshun94.util.Time.getMonthDays('2019', '02') );
console.log(8, io.github.shunshun94.util.Time.getMonthDays(new Date('2019/02/14')) );
console.log(9, io.github.shunshun94.util.Time.getMonthDays(2), '(これだけ「今年の2月」を対象としている)'); 

// 第一引数から第二引数の期間にある週末をリストアップ
const weekends = io.github.shunshun94.util.Time.getWeekendsInTerm(
    new Date('2019/1/1'),
    new Date('2020/1/1')
);
// => ※1 結果は追記部分記載

// 第一引数から第二引数の期間にある 10:00～14:00 の区間をリストアップ
const dayTimes = io.github.shunshun94.util.Time.getDaytimeTermInTerm(
    new Date('2019/1/1'),
    new Date('2020/1/1'),
    '10:00',
    '14:00'
);

// 第一引数から第二引数の期間にある 10:00～14:00 の区間をリストアップ (月～金除)
io.github.shunshun94.util.Time.getDaytimeTermInTerm(
    new Date('2019/1/1'),
    new Date('2020/1/1'),
    '10:00',
    '14:00',
    [1,2,3,4,5]
);

// 上述の weekends と dayTimes の重複する区間だけリストアップ
io.github.shunshun94.util.Time.getConflictedTerms(weekends, dayTimes);

スケジュールの重複などを扱わなければならない状況で便利かも。

※1 の結果

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    "headDate": "2019-01-04T15:00:00.000Z",
    "tailDate": "2019-01-06T15:00:00.000Z"
  },
  {
    "head": 1547218800000,
    "tail": 1547391600000,
    "headDate": "2019-01-11T15:00:00.000Z",
    "tailDate": "2019-01-13T15:00:00.000Z"
  },
  {
    "head": 1547823600000,
    "tail": 1547996400000,
    "headDate": "2019-01-18T15:00:00.000Z",
    "tailDate": "2019-01-20T15:00:00.000Z"
  },
  {
    "head": 1548428400000,
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    "headDate": "2019-01-25T15:00:00.000Z",
    "tailDate": "2019-01-27T15:00:00.000Z"
  },
  {
    "head": 1549033200000,
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    "headDate": "2019-02-01T15:00:00.000Z",
    "tailDate": "2019-02-03T15:00:00.000Z"
  },
  {
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    "headDate": "2019-02-08T15:00:00.000Z",
    "tailDate": "2019-02-10T15:00:00.000Z"
  },
  {
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    "headDate": "2019-02-15T15:00:00.000Z",
    "tailDate": "2019-02-17T15:00:00.000Z"
  },
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  },
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  },
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]