The Intl.NumberFormat.supportedLocalesOf() static method returns an array containing those of the provided locales that are supported in number formatting without having to fall back to the runtime's default locale.

Try it


Intl.NumberFormat.supportedLocalesOf(locales, options)



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

options Optional

An object that may have the following property:


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

Return value

An array of strings representing a subset of the given locale tags that are supported in number formatting without having to fall back to the runtime's default locale.


Using supportedLocalesOf()

Assuming a runtime that supports Indonesian and German but not Balinese in number formatting, supportedLocalesOf returns the Indonesian and German language tags unchanged, even though pinyin collation is neither relevant to number formatting nor used with Indonesian, and a specialized German for Indonesia is unlikely to be supported. Note the specification of the "lookup" algorithm here — a "best fit" matcher might decide that Indonesian is an adequate match for Balinese since most Balinese speakers also understand Indonesian, and therefore return the Balinese language tag as well.

const locales = ["ban", "id-u-co-pinyin", "de-ID"];
const options = { localeMatcher: "lookup" };
console.log(Intl.NumberFormat.supportedLocalesOf(locales, options));
// ["id-u-co-pinyin", "de-ID"]


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
supportedLocalesOf 24 12 29 15 10 25 56 14 10 1.5 4.4 1.8 13.0.0
0.12.0Before version 13.0.0, only the locale data for en-US is available by default. To make full ICU (locale) data available before version 13, see Node.js documentation on the --with-intl option and how to provide the data.

See also

© 2005–2023 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.