locales Optional

A string with a BCP 47 language tag or an Intl.Locale instance, or an array of such locale identifiers. For the general form and interpretation of the locales argument, see the parameter description on the Intl main page.

The following Unicode extension key is allowed:

nu

See numberingSystem.

This key can also be set with options (as listed below). When both are set, the options property takes precedence.

options Optional

An object containing the following properties, in the order they are retrieved (all of them are optional):

localeMatcher

The locale matching algorithm to use. Possible values are "lookup" and "best fit"; the default is "best fit". For information about this option, see Locale identification and negotiation.

numberingSystem

The numbering system to use for number formatting, such as "arab", "hans", "mathsans", and so on. For a list of supported numbering system types, see Intl.Locale.prototype.getNumberingSystems(). This option can also be set through the nu Unicode extension key; if both are provided, this options property takes precedence.

style

The style of the formatted duration. Possible values are:

"long"

E.g., 1 hour and 50 minutes

"short" (default)

E.g., 1 hr, 50 min

"narrow"

E.g., 1h 50m

"digital"

E.g., 1:50:00

years

The style of the formatted years. Possible values are "long", "short", and "narrow"; the default is options.style if it's not "digital", and "short" otherwise.

yearsDisplay

Whether to always display years, or only if nonzero. Possible values are "always" and "auto"; the default is "auto" if years is unspecified, and "always" otherwise.

months

The style of the formatted months. Possible values are "long", "short", and "narrow"; the default is options.style if it's not "digital", and "short" otherwise.

monthsDisplay

Whether to always display months, or only if nonzero. Possible values are "always" and "auto"; the default is "auto" if months is unspecified, and "always" otherwise.

weeks

The style of the formatted weeks. Possible values are "long", "short", and "narrow"; the default is options.style if it's not "digital", and "short" otherwise.

weeksDisplay

Whether to always display weeks, or only if nonzero. Possible values are "always" and "auto"; the default is "auto" if weeks is unspecified, and "always" otherwise.

days

The style of the formatted days. Possible values are "long", "short", and "narrow"; the default is options.style if it's not "digital", and "short" otherwise.

daysDisplay

Whether to always display days, or only if nonzero. Possible values are "always" and "auto"; the default is "auto" if days is unspecified, and "always" otherwise.

hours

The style of the formatted hours. Possible values are "long", "short", "narrow", "numeric", and "2-digit"; the default is options.style if it's not "digital", and "numeric" otherwise.

hoursDisplay

Whether to always display hours, or only if nonzero. Possible values are "always" and "auto"; the default is "auto" if hours is unspecified and options.style is not "digital", and "always" otherwise.

minutes

The style of the formatted minutes.

• If hours is "numeric" or "2-digit", possible values are "numeric" and "2-digit", and "numeric" is normalized to "2-digit"; the default is "numeric".
• Otherwise, possible values are "long", "short", "narrow", "numeric", and "2-digit"; the default is options.style if it's not "digital", and "numeric" otherwise.

minutesDisplay

Whether to always display minutes, or only if nonzero. Possible values are "always" and "auto"; the default is "auto" if minutes is unspecified and options.style is not "digital", and "always" otherwise.

seconds

The style of the formatted seconds.

• If minutes is "numeric" or "2-digit", possible values are "numeric" and "2-digit", and "numeric" is normalized to "2-digit"; the default is "numeric".
• Otherwise, possible values are "long", "short", "narrow", "numeric", and "2-digit"; the default is options.style if it's not "digital", and "numeric" otherwise.

secondsDisplay

Whether to always display seconds, or only if nonzero. Possible values are "always" and "auto"; the default is "auto" if seconds is unspecified and options.style is not "digital", and "always" otherwise.

milliseconds

The style of the formatted milliseconds.

• If seconds is "numeric" or "2-digit", the only possible value is "numeric"; the default is "numeric".
• Otherwise, possible values are "long", "short", "narrow", and "numeric"; the default is options.style if it's not "digital", and "numeric" otherwise.

millisecondsDisplay

Whether to always display milliseconds, or only if nonzero.

• If seconds is "numeric" or "2-digit", the only possible value is "auto"; the default is only "auto" when milliseconds is unspecified.
• Otherwise, possible values are "always" and "auto"; the default is "auto" if milliseconds is unspecified, and "always" otherwise.

microseconds

The style of the formatted microseconds.

• If milliseconds is "numeric", the only possible value is "numeric"; the default is "numeric".
• Otherwise, possible values are "long", "short", "narrow", and "numeric"; the default is options.style if it's not "digital", and "numeric" otherwise.

microsecondsDisplay

Whether to always display microseconds, or only if nonzero.

• If milliseconds is "numeric", the only possible value is "auto"; the default is only "auto" when microseconds is unspecified.
• Otherwise, possible values are "always" and "auto"; the default is "auto" if microseconds is unspecified, and "always" otherwise.

nanoseconds

The style of the formatted nanoseconds.

• If microseconds is "numeric", the only possible value is "numeric"; the default is "numeric".
• Otherwise, possible values are "long", "short", "narrow", and "numeric"; the default is options.style if it's not "digital", and "numeric" otherwise.

nanosecondsDisplay

Whether to always display nanoseconds, or only if nonzero.

• If microseconds is "numeric", the only possible value is "auto"; the default is only "auto" when nanoseconds is unspecified.
• Otherwise, possible values are "always" and "auto"; the default is "auto" if nanoseconds is unspecified, and "always" otherwise.

fractionalDigits

Number of how many fractional second digits to display in the output. Possible values are from 0 to 9; the default is undefined (include as many fractional digits as necessary).

RangeError

Thrown if locales or options contain invalid values.

For each time segment, an Intl.NumberFormat object is constructed under the hood. It uses the following options (see Intl.NumberFormat() for details):

• numberingSystem: the value of options.numberingSystem

When milliseconds, microseconds, or nanoseconds uses the "numeric" style, the following options are also used:

• minimumFractionDigits: 0 when options.fractionalDigits is undefined, options.fractionalDigits otherwise
• maximumFractionDigits: 9 when options.fractionalDigits is undefined, options.fractionalDigits otherwise
• roundingMode: "trunc"

When the time segment uses the "2-digit" style, the following options are also used:

• minimumIntegerDigits: 2

When the time segment uses the "long", "short", or "narrow" style, the following options are also used:

• style: "unit" when "long", "short", or "narrow" is specified, undefined otherwise
• unit: the currently formatted unit ("years", "days", "nanoseconds", etc.)
• unitDisplay: the value of the time segment style ("long", "short", or "narrow")

• Intl.DurationFormat
• Intl.supportedValuesOf()
• Intl