Temporal.Duration.prototype.add()

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 add() method of Temporal.Duration instances returns a new Temporal.Duration object with the sum of this duration and a given duration. The result is balanced.

Syntax

add(other)

Parameters

other: A string, an object, or a Temporal.Duration instance representing a duration to add to this duration. It is converted to a Temporal.Duration object using the same algorithm as Temporal.Duration.from().

Return value

A new Temporal.Duration object representing the sum of this duration and other.

Exceptions

RangeError

Thrown in one of the following cases:

Either this or other is a calendar duration (it has a non-zero years, months, or weeks), because calendar durations are ambiguous without a calendar and time reference.
The sum of this and other overflows the maximum or underflows the minimum representable duration, which is ±2⁵³ seconds.

Description

Non-calendar durations unambiguously represent a fixed amount of time. Internally, this and other are both converted to nanoseconds (assuming 24-hour days) and added together. The result is then converted back to a Temporal.Duration object, so the result is always balanced with the largest possible unit being days.

If you want to perform addition or subtraction with a calendar duration, you can add both durations to a starting point and then figure out the difference between the two resulting instants; that is, dur1 + dur2 is equivalent to (start + dur1 + dur2) - start.

To add a duration to a date or time, use the add() method of the date or time object instead.

Examples

Using add()

const d1 = Temporal.Duration.from({ hours: 1, minutes: 30 });
const d2 = Temporal.Duration.from({ hours: -1, minutes: -20 });

const d3 = d1.add(d2);
console.log(d3.toString()); // "PT10M"

Adding calendar durations

const d1 = Temporal.Duration.from({ days: 1 });
const d2 = Temporal.Duration.from({ months: 1 });

d1.add(d2); // RangeError: can't compare durations when "relativeTo" is undefined

const start = Temporal.PlainDateTime.from("2022-01-01T00:00"); // ISO 8601 calendar
const result = start.add(d1).add(d2).since(start);
console.log(result.toString()); // "P32D"

Specifications

Specification
Temporal proposal # sec-temporal.duration.prototype.add

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
`add`	No	No	No	No	No	No	No	No	No	No	No	1.40	No