Temporal.PlainDateTime.prototype.round()

The round() method of PlainDateTime instances returns a new Temporal.PlainDateTime object representing this date-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. For all values of smallestUnit except "day", the increment must be a divisor of the maximum value of the unit; 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. For "day", the increment must be 1.
    • 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: "day", "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 PlainDateTime object representing this date-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 dt = Temporal.PlainDateTime.from("2021-07-01T12:34:56.123456789");
const nearestMillisecond = dt.round("millisecond");
console.log(nearestMillisecond.toString()); // 2021-07-01T12:34:56.123

const nearestHalfHour = dt.round({
  smallestUnit: "minute",
  roundingIncrement: 30,
});
console.log(nearestHalfHour.toString()); // 2021-07-01T12:30:00

const nextDay = dt.round({ smallestUnit: "day", roundingMode: "ceil" });
console.log(nextDay.toString()); // 2021-07-02T00:00:00

Specifications

Browser compatibility

See also

• PlainDateTime