The of() method of Intl.DisplayNames instances receives a code and returns a string based on the locale and options provided when instantiating this Intl.DisplayNames object.

Try it

const regionNamesInEnglish = new Intl.DisplayNames(["en"], { type: "region" });
const regionNamesInTraditionalChinese = new Intl.DisplayNames(["zh-Hant"], {
  type: "region",
});

console.log(regionNamesInEnglish.of("US"));
// Expected output: "United States"

console.log(regionNamesInTraditionalChinese.of("US"));
// Expected output: "美國"

Syntax

of(code)

Parameters

code

The code to provide depends on the type:

• If the type is "region", code should be either a two-letter ISO 3166 region code, or a three-digit UN M49 geographic region. It is required to follow the unicode_region_subtag grammar. Use uppercase codes (e.g., "US"), because lowercase ones (e.g., "us") may not work reliably everywhere.
• If the type is "script", code should be a four-letter ISO 15924 script code. It is required to follow the unicode_script_subtag grammar.
• If the type is "language", code should be matched by the unicode_language_id nonterminal.
• If the type is "currency", code should be a three-letter ISO 4217 currency code. It is required to have exactly three alphabetic characters.
• If the type is "dateTimeField", code should be one of: "era", "year", "quarter", "month", "weekOfYear", "weekday", "day", "dayPeriod", "hour", "minute", "second", "timeZoneName".
• If the type is "calendar", code should be a calendar key. It is required to follow the type grammar of a Unicode locale identifier.

Return value

A language-specific formatted string, or undefined if there's no data for the input and fallback is "none".

Exceptions

RangeError

Thrown if code is not structurally valid for the given type.

Examples

Using the of method

const regionNames = new Intl.DisplayNames("en", { type: "region" });
regionNames.of("419"); // "Latin America"

const languageNames = new Intl.DisplayNames("en", { type: "language" });
languageNames.of("fr"); // "French"

const currencyNames = new Intl.DisplayNames("en", { type: "currency" });
currencyNames.of("EUR"); // "Euro"

const languageNamesStandard = new Intl.DisplayNames("fr", {
  type: "language",
  languageDisplay: "standard",
});
languageNamesStandard.of("fr-CA"); // "français (Canada)"

const languageNamesDialect = new Intl.DisplayNames("fr", {
  type: "language",
  languageDisplay: "dialect",
});
languageNamesDialect.of("fr-CA"); // "français canadien"

Using fallback

When the Intl.DisplayNames is constructed with fallback: "code", the of() method will return the code if the input looks structurally valid but there's no data for the input. If fallback is "none", undefined is returned.

console.log(
  new Intl.DisplayNames("en", { type: "region", fallback: "code" }).of("ZL"),
); // "ZL"

console.log(
  new Intl.DisplayNames("en", { type: "region", fallback: "none" }).of("ZL"),
); // undefined

However, this only applies if the code is structurally valid. For example, if type is "region" but code does not follow the unicode_region_subtag grammar (2 alphabetic characters or 3 numeric characters), a RangeError is directly thrown instead of using the fallback.

console.log(
  new Intl.DisplayNames("en", { type: "region", fallback: "code" }).of("ZLC"),
); // throws RangeError: invalid value "ZLC" for option region

Specifications

Browser compatibility

See also

• Intl.DisplayNames