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 or top-heavy 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: for calendar duration arithmetic, use date arithmetic relative to a starting point

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

Browser compatibility

See also

• Temporal.Duration
• Temporal.Duration.prototype.subtract()