Temporal.PlainTime.prototype.round()

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 round() method of Temporal.PlainTime instances returns a new Temporal.PlainTime object representing this time rounded to the given unit.

Syntax

round(smallestUnit)
round(options)

Parameters

smallestUnit

A string representing the smallestUnit option. This is a convenience overload, so round(smallestUnit) is equivalent to round({ smallestUnit }), where smallestUnit is a string.

options

An object containing some or all of the following properties (in the order they are retrieved and validated):

roundingIncrement Optional: A number (truncated to an integer) representing the rounding increment in the given smallestUnit. Defaults to 1. The increment must be a divisor of the maximum value of smallestUnit; for example, if the unit is hours, the increment must be a divisor of 24 and must not be 24 itself, which means it can be 1, 2, 3, 4, 6, 8, or 12.
roundingMode Optional: A string specifying how to round off the fractional part of smallestUnit. See Intl.NumberFormat(). Defaults to "halfExpand".
smallestUnit: A string representing the smallest unit to include in the output. The value must be one of the following: "hour", "minute", "second", "millisecond", "microsecond", "nanosecond", or their plural forms. For units larger than "nanosecond", fractional parts of the smallestUnit will be rounded according to the roundingIncrement and roundingMode settings.

Return value

A new Temporal.PlainTime object representing this time rounded to the given unit, where all units smaller than smallestUnit are zeroed out.

Exceptions

RangeError: Thrown if any of the options is invalid.

Examples

Rounding off small units

const time = Temporal.PlainTime.from("12:34:56.123456789");
const nearestMillisecond = time.round("millisecond");
console.log(nearestMillisecond.toString()); // 12:34:56.123

const nearestHalfHour = time.round({
  smallestUnit: "minute",
  roundingIncrement: 30,
});
console.log(nearestHalfHour.toString()); // 12:30:00

const nextHour = time.round({ smallestUnit: "hour", roundingMode: "ceil" });
console.log(nextHour.toString()); // 13:00:00

Specifications

Specification
Temporal proposal # sec-temporal.plaintime.prototype.round

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
`round`	No	No	No	No	preview	No	No	No	No	No	No	1.40	No