Temporal.PlainMonthDay.prototype.valueOf()

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

Browser compatibility

See also

• Temporal.PlainMonthDay
• Temporal.PlainMonthDay.prototype.toString()
• Temporal.PlainMonthDay.prototype.toJSON()
• Temporal.PlainMonthDay.prototype.toLocaleString()