The Intl.ListFormat.supportedLocalesOf() static method returns an array containing those of the provided locales that are supported in list formatting without having to fall back to the runtime's default locale.
Syntax
Intl.ListFormat.supportedLocalesOf(locales)
Intl.ListFormat.supportedLocalesOf(locales, options)
Parameters
locales- : A string with a BCP 47 language tag, or an array of such strings. For the general form and interpretation of the
localesargument, see the parameter description on theIntlmain page.
- : A string with a BCP 47 language tag, or an array of such strings. For the general form and interpretation of the
options- : An object that may have the following property:
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 the Intl page.
- : The locale matching algorithm to use. Possible values are
- : An object that may have the following property:
Return value
An array of strings representing a subset of the given locale tags that are supported in list formatting without having to fall back to the runtime's default locale.
Examples
Using supportedLocalesOf()
Assuming a runtime that supports Indonesian and German but not Balinese in list formatting, supportedLocalesOf returns the Indonesian and German language tags unchanged, even though pinyin collation is neither relevant to list 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.ListFormat.supportedLocalesOf(locales, options));
// ["id-u-co-pinyin", "de-ID"]