jQuery DatePicker UI regional Default - how to set based on condition

Question

I am aware that we can localize datepicker using

$(selector).datepicker($.datepicker.regional['fr']);

However can we do something like if a user passes in a value that's not supported by the datepicker regional, then automatically shift to the default language

Something like:

if(datepicker.regional does not support the language)
    $.datepicker.setDefaults($.datepicker.regional['']);