date-fns/src/_lib/startOfUTCISOWeekYear/index.js


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import getUTCISOWeekYear from '../getUTCISOWeekYear/index'
import startOfUTCISOWeek from '../startOfUTCISOWeek/index'
import requiredArgs from '../requiredArgs/index'

// This function will be a part of public API when UTC function will be implemented.
// See issue: https://github.com/date-fns/date-fns/issues/376
export default function startOfUTCISOWeekYear(dirtyDate) {
  requiredArgs(1, arguments)

  var year = getUTCISOWeekYear(dirtyDate)
  var fourthOfJanuary = new Date(0)
  fourthOfJanuary.setUTCFullYear(year, 0, 4)
  fourthOfJanuary.setUTCHours(0, 0, 0, 0)
  var date = startOfUTCISOWeek(fourthOfJanuary)
  return date
}