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import toInteger from '../_lib/toInteger/index.ts'import toDate from '../toDate/index.ts'import requiredArgs from '../_lib/requiredArgs/index.ts'
/** * @name addMonths * @category Month Helpers * @summary Add the specified number of months to the given date. * * @description * Add the specified number of months to the given date. * * ### v2.0.0 breaking changes: * * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes). * * @param {Date|Number} date - the date to be changed * @param {Number} amount - the amount of months to be added. Positive decimals will be rounded using `Math.floor`, decimals less than zero will be rounded using `Math.ceil`. * @returns {Date} the new date with the months added * @throws {TypeError} 2 arguments required * * @example * // Add 5 months to 1 September 2014: * const result = addMonths(new Date(2014, 8, 1), 5) * //=> Sun Feb 01 2015 00:00:00 */export default function addMonths(  dirtyDate: Date | number,  dirtyAmount: number): Date {  requiredArgs(2, arguments)
  const date = toDate(dirtyDate)  const amount = toInteger(dirtyAmount)  if (isNaN(amount)) {    return new Date(NaN)  }  if (!amount) {    // If 0 months, no-op to avoid changing times in the hour before end of DST    return date  }  const dayOfMonth = date.getDate()
  // The JS Date object supports date math by accepting out-of-bounds values for  // month, day, etc. For example, new Date(2020, 0, 0) returns 31 Dec 2019 and  // new Date(2020, 13, 1) returns 1 Feb 2021.  This is *almost* the behavior we  // want except that dates will wrap around the end of a month, meaning that  // new Date(2020, 13, 31) will return 3 Mar 2021 not 28 Feb 2021 as desired. So  // we'll default to the end of the desired month by adding 1 to the desired  // month and using a date of 0 to back up one day to the end of the desired  // month.  const endOfDesiredMonth = new Date(date.getTime())  endOfDesiredMonth.setMonth(date.getMonth() + amount + 1, 0)  const daysInMonth = endOfDesiredMonth.getDate()  if (dayOfMonth >= daysInMonth) {    // If we're already at the end of the month, then this is the correct date    // and we're done.    return endOfDesiredMonth  } else {    // Otherwise, we now know that setting the original day-of-month value won't    // cause an overflow, so set the desired day-of-month. Note that we can't    // just set the date of `endOfDesiredMonth` because that object may have had    // its time changed in the unusual case where where a DST transition was on    // the last day of the month and its local time was in the hour skipped or    // repeated next to a DST transition.  So we use `date` instead which is    // guaranteed to still have the original time.    date.setFullYear(      endOfDesiredMonth.getFullYear(),      endOfDesiredMonth.getMonth(),      dayOfMonth    )    return date  }}