Negotiates the languages between the list of requested locales against a list of available locales.

It accepts three arguments:

requestedLocales: an Array of strings with BCP47 locale IDs sorted according to user preferences.

availableLocales: an Array of strings with BCP47 locale IDs of locale for which resources are available. Unsorted.

options: An object with the following, optional keys:

  strategy: 'filtering' (default) | 'matching' | 'lookup'

  defaultLocale:
    a string with BCP47 locale ID to be used
    as a last resort locale.

It returns an Array of strings with BCP47 locale IDs sorted according to the user preferences.

The exact list will be selected differently depending on the strategy:

'filtering': (default) In the filtering strategy, the algorithm will attempt to match as many keys in the available locales in order of the requested locales.

'matching': In the matching strategy, the algorithm will attempt to find the best possible match for each element of the requestedLocales list.

'lookup': In the lookup strategy, the algorithm will attempt to find a single best available locale based on the requested locales list.

This strategy requires defaultLocale option to be set.