JavaScript for detecting browser language preference [duplicate]

Answer 1

For who are looking for Java Server solution

Here is RestEasy

@GET
@Path("/preference-language")
@Consumes({"application/json", "application/xml"})
@Produces({"application/json", "application/xml"})
public Response getUserLanguagePreference(@Context HttpHeaders headers) {
    return Response.status(200)
            .entity(headers.getAcceptableLanguages().get(0))
            .build();
}