dayjs-plugin-utc/src/UTCDate.js

utc plugin for dayjs

import { padZoneStr } from './util'

export const LOCAL_TIMEZONE_OFFSET = new Date().getTimezoneOffset()
const datePrototype = Date.prototype

function getTimestampOffset(timezoneOffset, pastTimezoneOffset = LOCAL_TIMEZONE_OFFSET) {
  return (timezoneOffset - pastTimezoneOffset) * 60000
}

class UTCDate {
  constructor(arg = new Date(), $timezoneOffset = arg.getTimezoneOffset()) {
    this.$d = new Date(arg.getTime() - getTimestampOffset($timezoneOffset))
    this.$timezoneOffset = $timezoneOffset
  }

  getTimezoneOffset() {
    return this.$timezoneOffset
  }

  setTimezoneOffset($timezoneOffset = this.$timezoneOffset) {
    this.$d.setTime(this.$d.getTime() + getTimestampOffset(this.$timezoneOffset, $timezoneOffset))
    this.$timezoneOffset = $timezoneOffset
  }
}

[
  'toDateString', 'toLocaleString', 'toLocaleDateString', 'toLocaleTimeString',
  'setDate', 'setFullYear', 'setHours', 'setMilliseconds', 'setMinutes', 'setMonth', 'setSeconds', 'setTime', 'setYear',
  'getDate', 'getDay', 'getFullYear', 'getHours', 'getMilliseconds', 'getMinutes', 'getMonth', 'getSeconds', 'getYear'
].forEach((key) => {
  UTCDate.prototype[key] = function () {
    // eslint-disable-next-line prefer-rest-params
    return datePrototype[key].apply(this.$d, arguments)
  }
});

[
  'toISOString', 'toUTCString', 'toGMTString', 'toJSON', 'getUTCDate', 'getUTCDay', 'getUTCFullYear', 'getUTCHours', 'getUTCMilliseconds', 'getUTCMinutes', 'getUTCMonth', 'getUTCSeconds', 'valueOf', 'getTime'
].forEach((key) => {
  UTCDate.prototype[key] = function () {
    return datePrototype[key].apply(
      new Date(this.$d.getTime() + getTimestampOffset(this.$timezoneOffset)),
      arguments // eslint-disable-line prefer-rest-params
    )
  }
});

[
  'setUTCDate', 'setUTCFullYear', 'setUTCHours', 'setUTCMilliseconds', 'setUTCMinutes', 'setUTCMonth', 'setUTCSeconds'
].forEach((key) => {
  UTCDate.prototype[key] = function () {
    const tmp = new Date(this.$d.getTime() + getTimestampOffset(this.$timezoneOffset))
    // eslint-disable-next-line prefer-rest-params
    datePrototype[key].apply(tmp, arguments)
    tmp.setTime(tmp.getTime() - getTimestampOffset(this.$timezoneOffset))
    this.$d = tmp
  }
});

[
  'toString', 'toTimeString'
].forEach((key) => {
  UTCDate.prototype[key] = function () {
    // eslint-disable-next-line prefer-rest-params
    return datePrototype[key].apply(this.$d, arguments).replace(/GMT(.*)$/, `GMT${padZoneStr(this.$timezoneOffset)}`)
  }
})

export default UTCDate