The code to provide depends on the type passed to display name during creation:
"region", code should be either an ISO-3166 two letters region code,
or a three digits UN M49 Geographic Regions."script", code should be an ISO-15924 four letters script code."language", code should be a languageCode ["-" scriptCode] ["-" regionCode ] *("-" variant )
subsequence of the unicode_language_id grammar in UTS 35's Unicode Language and Locale Identifiers grammar.
languageCode is either a two letters ISO 639-1 language code or a three letters ISO 639-2 language code."currency", code should be a 3-letter ISO 4217 currency code.MDN.
Returns a new object with properties reflecting the locale and style formatting options computed during the construction of the current
Intl/DisplayNames object.
MDN.
Receives a code and returns a string based on the locale and options provided when instantiating
Intl.DisplayNames()