Temporal.PlainYearMonth.prototype.equals()

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The equals() method of Temporal.PlainYearMonth instances returns true if this year-month is equivalent in value to another year-month (in a form convertible by 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 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 Temporal.PlainYearMonth.from() method, but can be set manually using the 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

js
equals(other)

Parameters

other

A string, an object, or a Temporal.PlainYearMonth instance representing the other year-month to compare. It is converted to a Temporal.PlainYearMonth object using the same algorithm as 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()

js
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

Specification
Temporal proposal
# sec-temporal.plainyearmonth.prototype.equals

Browser compatibility

BCD tables only load in the browser

See also