Temporal.PlainMonthDay.prototype.valueOf()

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 valueOf() method of Temporal.PlainMonthDay instances throws a TypeError, which prevents Temporal.PlainMonthDay instances from being implicitly converted to primitives when used in arithmetic or comparison operations.

Syntax

valueOf()

Parameters

None.

Return value

None.

Exceptions

TypeError: Always thrown.

Description

Because both primitive conversion and number conversion call valueOf() before toString(), if valueOf() is absent, then an expression like monthDay1 > monthDay2 would implicitly compare them as strings, which may have unexpected results. By throwing a TypeError, Temporal.PlainMonthDay instances prevent such implicit conversions. You need to explicitly convert them to strings using Temporal.PlainMonthDay.prototype.toString().

Examples

Arithmetic and comparison operations on Temporal.PlainMonthDay

All arithmetic and comparison operations on Temporal.PlainMonthDay instances should use the dedicated methods or convert them to primitives explicitly.

const md1 = Temporal.PlainMonthDay.from("01-01");
const md2 = Temporal.PlainMonthDay.from("07-01");
md1 > md2; // TypeError: can't convert PlainMonthDay to primitive type
Temporal.PlainDate.compare(
  md1.toPlainDate({ year: 2021 }),
  md2.toPlainDate({ year: 2021 }),
); // -1

md2 - md1; // TypeError: can't convert PlainMonthDay to primitive type
md2
  .toPlainDate({ year: 2021 })
  .since(md1.toPlainDate({ year: 2021 }))
  .toString(); // "P181D"

Specifications

Specification
Temporal proposal # sec-temporal.plainmonthday.prototype.valueof

Browser compatibility

	Desktop					Mobile						Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	Deno	Node.js
`valueOf`	No	No	No	No	No	No	No	No	No	No	No	1.40	No