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Diffstat (limited to 'node_modules/date-fns/esm/addMonths/index.js')
| -rw-r--r-- | node_modules/date-fns/esm/addMonths/index.js | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/node_modules/date-fns/esm/addMonths/index.js b/node_modules/date-fns/esm/addMonths/index.js new file mode 100644 index 0000000..f5c0eb1 --- /dev/null +++ b/node_modules/date-fns/esm/addMonths/index.js @@ -0,0 +1,61 @@ +import toInteger from "../_lib/toInteger/index.js"; +import toDate from "../toDate/index.js"; +import requiredArgs from "../_lib/requiredArgs/index.js"; +/** + * @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. + * + * @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, dirtyAmount) { + requiredArgs(2, arguments); + var date = toDate(dirtyDate); + var 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; + } + var 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. + var endOfDesiredMonth = new Date(date.getTime()); + endOfDesiredMonth.setMonth(date.getMonth() + amount + 1, 0); + var 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; + } +}
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