Usage of date-fns

Examples

• startOfToday()

Returns a Date object with today's date, starting at 00:00 AM.

let today = startOfToday();

console.log(today);
// Mon Mar 27 2023 00:00:00 GMT+0700 (Western Indonesia Time)

• format()

Accepts Date or number as first argument and string format as second argument. Returns a Date object or number.

let currentMonth = format(today, "MMM-yyyy");

console.log(currentMonth);
// Mar-2023

• parse()

Accepts dateString as first argument, string format as second argument, and referenceDate as third argument, which could be a Date object or a number. Returns a Date object or number.

let firstDayCurrentMonth = parse(currentMonth, "MMM-yyyy", new Date());

console.log(firstDayCurrentMonth);
// Wed Mar 01 2023 00:00:00 GMT+0700 (Western Indonesia Time)

• startOfMonth() & endOfMonth()

Accepts Date as first argument, returns a Date object.

console.log(startOfMonth(firstDayCurrentMonth));
// Wed Mar 01 2023 00:00:00 GMT+0700 (Western Indonesia Time)

console.log(endOfMonth(firstDayCurrentMonth));
// Fri Mar 31 2023 23:59:59 GMT+0700 (Western Indonesia Time)

• add()

Increments date by a duration time provided in the second argument.

Accepts Date as first argument and Duration object as second argument. Returns a Date object.

console.log(add(firstDayCurrentMonth, { days: 1 }));
// Thu Mar 02 2023 00:00:00 GMT+0700 (Western Indonesia Time)

• eachDayOfInterval()

Returns an Array of Date object.

Accepts Interval as first argument, which consists of start and end field that determines the final output.

let days = eachDayOfInterval({
  start: firstDayCurrentMonth,
  end: add(firstDayCurrentMonth, { days: 1 }),
});

console.log(days);
/* 
Array [
0: Date Wed Mar 01 2023 00:00:00 GMT+0700 (Western Indonesia Time)
1: Date Thu Mar 02 2023 00:00:00 GMT+0700 (Western Indonesia Time)] 
*/

• parseISO()

Parses an ISO String and returns a Date object.

Equivalent as calling new Date()

console.log(parseISO("2023-03-28T13:00"));
// Date Tue Mar 28 2023 13:00:00 GMT+0700 (Western Indonesia Time)

console.log(new Date("2023-03-28T13:00"));
// Date Tue Mar 28 2023 13:00:00 GMT+0700 (Western Indonesia Time)

• isToday()

Returns Day, which is a union type of 0 | 1 | 2 | 3 | 4 | 5 | 6, with 0 being Monday, 1 being Tuesday, etc.

Accepts a Date object or number as first argument.

console.log(isToday(today));
// true

let tomorrow = add(today, { days: 1 });

console.log(isToday(tomorrow));
// false

• isEqual(), isSameMonth(), isSameDay()

Compares two arguments based on the name of the function itself, dateLeft and dateRight, both either a Date object or a number. Returns a boolean.

let todayWithOneHourAdded = add(today, {
  hours: 1,
});

console.log(isEqual(today, todayWithOneHourAdded));
// false

console.log(isSameMonth(today, firstDayCurrentMonth));
// true

console.log(isSameDay(today, todayWithOneHourAdded));
// true

• startOfWeek() and endOfWeek()

Returns a Date object or number, either the start or end of week based on the function used. Accepts a Date object or number as first argument. Useful when working with calendars that need dates outside of the current month.

console.log(startOfWeek(firstDayCurrentMonth));
// Date Sun Feb 26 2023 00:00:00 GMT+0700 (Western Indonesia Time)

console.log(endOfWeek(endOfMonth(firstDayCurrentMonth)));
// Date Sat Apr 01 2023 23:59:59 GMT+0700 (Western Indonesia Time)