AddressErrors.languageCode - Web APIs
an object based on addresserrors includes a languagecode property when the address's languagecode property couldn't be validated.
... syntax var languageerror = addresserrors.languagecode; value if the value specified in the paymentaddress object's languagecode property could not be validated, this property contains a domstring offering a human-readable explanation of the validation error and offers suggestions for correcting it.
... if the languagecode value was validated successfully, this property is not included in the addresserrors object.
... specifications specification status comment payment request apithe definition of 'addresserrors.languagecode' in that specification.

PaymentAddress.languageCode - Web APIs
the languagecode read-only property of the paymentaddress interface returns a string containing the bcp-47 language code for the address.
... syntax var paymentlanguagecode = paymentaddress.languagecode; value a domstring providing the bcp-47 format language code indicating the language the address was written in, such as "en-us", "pt-br", or "ja-jp".

Index - Web APIs
34 addresserrors.languagecode api, address, addresserrors, deprecated, language, languagecode, locale, payment request, payment request api, property, reference, payment an object based on addresserrors includes a languagecode property when the address's languagecode property couldn't be validated.
... 2903 paymentaddress.languagecode api, address, deprecated, language, languagecode, locale, rtcrtpstreamstats, rtp, reference, statistics, stats, webrtc, webrtc api, rtc the languagecode read-only property of the paymentaddress interface returns a string containing the bcp-47 language code for the address.

Intl.DisplayNames.prototype.of() - JavaScript
if the type is "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.

AddressErrors - Web APIs
languagecode a domstring which, if present, indicates that the languagecode property of the paymentaddress could not be validated.

PaymentAddress - Web APIs
paymentaddress.languagecode read only a domstring indicating the language code of the address.