javascript - 从对象数组中获取本月的第一天

Question

如果今天是 2018-11-28，我有一个这样的对象数组:

  const dataset = [
  {
    "timestamp": "2018-11-28T16:38:07.610Z",
    "value": 751.998557581834
  },
  {
    "timestamp": "2018-11-27T16:38:07.610Z",
    "value": 644.9987628195244
  },
  {
    "timestamp": "2018-11-26T16:38:07.610Z",
    "value": 766.9985288101943
  },
  {
    "timestamp": "2018-11-25T16:38:07.610Z",
    "value": 953.9981701237627
  },
  {
    "timestamp": "2018-11-24T16:38:07.610Z",
    "value": 912.9982487662423
  },
  {
    "timestamp": "2018-11-23T16:38:07.610Z",
    "value": 402
  },
  {
    "timestamp": "2018-11-22T16:38:07.610Z",
    "value": 914.9982449300243
  },
  {
    "timestamp": "2018-11-21T16:38:07.610Z",
    "value": 769.9985230558668
  },
  {
    "timestamp": "2018-11-20T16:38:07.610Z",
    "value": 772.9985173015398
  },
  {
    "timestamp": "2018-11-19T16:38:07.610Z",
    "value": 176
  },
  {
    "timestamp": "2018-11-18T16:38:07.610Z",
    "value": 978.9981221710306
  },
  {
    "timestamp": "2018-11-17T16:38:07.611Z",
    "value": 342
  },
  {
    "timestamp": "2018-11-16T16:38:07.611Z",
    "value": 498.9990428634777
  },
  {
    "timestamp": "2018-11-15T16:38:07.611Z",
    "value": 326
  },
  {
    "timestamp": "2018-11-14T16:38:07.612Z",
    "value": 649.9987532289786
  },
  {
    "timestamp": "2018-11-13T16:38:07.612Z",
    "value": 70
  },
  {
    "timestamp": "2018-11-12T16:38:07.612Z",
    "value": 349
  },
  {
    "timestamp": "2018-11-11T16:38:07.612Z",
    "value": 191
  },
  {
    "timestamp": "2018-11-10T16:38:07.612Z",
    "value": 154
  },
  {
    "timestamp": "2018-11-09T16:38:07.613Z",
    "value": 109
  },
  {
    "timestamp": "2018-11-08T16:38:07.613Z",
    "value": 237
  },
  {
    "timestamp": "2018-11-07T16:38:07.613Z",
    "value": 398
  },
  {
    "timestamp": "2018-11-06T16:38:07.613Z",
    "value": 606.9988357076774
  },
  {
    "timestamp": "2018-11-05T16:38:07.614Z",
    "value": 131
  },
  {
    "timestamp": "2018-11-04T16:38:07.614Z",
    "value": 397
  },
  {
    "timestamp": "2018-11-03T16:38:07.614Z",
    "value": 583.9988798241893
  },
  {
    "timestamp": "2018-11-02T16:38:07.614Z",
    "value": 362
  },
  {
    "timestamp": "2018-11-01T16:38:07.614Z",
    "value": 686.998682258936
  },
  {
    "timestamp": "2018-10-31T16:38:07.614Z",
    "value": 131
  },
  {
    "timestamp": "2018-10-30T16:38:07.614Z",
    "value": 212
  }
]

对象是使用以下代码创建的:

  import { DateTime } from 'luxon'

  const timestamp = startDate.minus({ days: i }).toJSDate()
  return { timestamp: timestamp, value: randomValue }

我想要包含本月第一天的对象，所以在这个例子中，我想要:

  {
    "timestamp": "2018-11-01T16:38:07.614Z",
    "value": 686.998682258936
  }

这是我尝试过的:

const date = new Date()
const firstDayOfThisMonth = new Date(date.getFullYear(), date.getMonth(), 1)
const firstDayOfThisMonthSub = firstDayOfThisMonth.toString().substring(0, 15)
const bo = dataset.map((d, i) => {
  const sub = d.toString().substring(0, 15)
  if (sub === firstDayOfThisMonthSub) return d
})

它不起作用(我得到一个 undefined 数组)，我希望有更聪明的方法来做到这一点。 我可以使用 Javascript Date 对象或 Luxon图书馆。

谢谢

Answer 1

与 luxon :

const firstDayOfThisMonth = DateTime.local().startOf('month')
const firstDayRecord = dataset.find(record => {
 return DateTime.fromISO(record.timestamp).hasSame(firstDayOfThisMonth, 'day')
})

这应该可以解决问题