Intl.Locale.prototype.language

Language is one of the core attributes of a locale. The Unicode specification treats the language identifier of a locale as the language and the region together (to make a distinction between dialects and variations, e.g., British English vs. American English). The language property of a Intl.Locale returns strictly the locale's language subtag. The language property's value is set at construction time, either through the language subtag (first part) of the locale identifier or through the language option of the Intl.Locale() constructor. The latter takes priority if they are both present.

The set accessor of language is undefined. You cannot change this property directly.

Like other locale subtags, the language can be added to the Intl.Locale object via the locale string, or a configuration object argument to the constructor.

In order to be a valid Unicode locale identifier, a string must start with the language subtag. The main argument to the Intl.Locale() constructor must be a valid Unicode locale identifier, so whenever the constructor is used, it must be passed an identifier with a language subtag.

const locale = new Intl.Locale("en-Latn-US");
console.log(locale.language); // Prints "en"

While the language subtag must be specified, the Intl.Locale() constructor has an optional configuration object argument, which can override the language subtag.

const locale = new Intl.Locale("en-Latn-US", { language: "es" });
console.log(locale.language); // Prints "es"

• Intl.Locale
• Unicode language subtag in the Unicode locale data markup language spec