Temporal.PlainYearMonth.prototype.equals()

The equals() method of {{jsxref("Temporal.PlainYearMonth")}} instances returns true if this year-month is equivalent in value to another year-month (in a form convertible by {{jsxref("Temporal/PlainYearMonth/from", "Temporal.PlainYearMonth.from()")}}), and false otherwise. They are compared both by their underlying ISO date values and their calendars, so two year-months from different calendars may be considered equal by {{jsxref("Temporal/PlainYearMonth/compare", "Temporal.PlainYearMonth.compare()")}} but not by equals().

[!NOTE] PlainYearMonth objects keep track of a reference ISO day, which is also used in the comparison. This day is automatically set when using the {{jsxref("Temporal/PlainYearMonth/from", "Temporal.PlainYearMonth.from()")}} method, but can be set manually using the {{jsxref("Temporal/PlainYearMonth/PlainYearMonth", "Temporal.PlainYearMonth()")}} constructor, causing two equivalent year-months to be considered different if they have different reference days. For this reason, you should avoid using the constructor directly and prefer the from() method.

Syntax#

equals(other)

Parameters#

• other
• : A string, an object, or a {{jsxref("Temporal.PlainYearMonth")}} instance representing the other year-month to compare. It is converted to a Temporal.PlainYearMonth object using the same algorithm as {{jsxref("Temporal/PlainYearMonth/from", "Temporal.PlainYearMonth.from()")}}.

Return value#

true if this year-month is equal to other both in their date value and their calendar, false otherwise.

Examples#

Using equals()#

const ym1 = Temporal.PlainYearMonth.from("2021-08");
const ym2 = Temporal.PlainYearMonth.from({ year: 2021, month: 8 });
console.log(ym1.equals(ym2)); // true

const ym3 = Temporal.PlainYearMonth.from("2021-08-01[u-ca=japanese]");
console.log(ym1.equals(ym3)); // false

const ym4 = Temporal.PlainYearMonth.from("2021-09");
console.log(ym1.equals(ym4)); // false

Specifications#

{{Specifications}}

Browser compatibility#

{{Compat}}

See also#

• {{jsxref("Temporal.PlainYearMonth")}}
• {{jsxref("Temporal/PlainYearMonth/compare", "Temporal.PlainYearMonth.compare()")}}