Formtastic errors w/ ajax + knockout.js and responds_to :json

application.js

$.ajax({
  error: function(jqXHR, textStatus, errorThrown) {
    // reset
    $('.formtastic li').removeClass("error");
    $('.formtastic li .inline-errors').remove();

    // set the errors
    // TODO turn into dynamic 
    // TODO include errors for :base and #semantic_errors
    var errors = ko.mapping.toJS(ko.mapping.fromJSON(jqXHR.responseText));
    $.each(errors, function(key, value) {
      $(".formtastic.menu li#menu_"+key+"_input.required").addClass("error");
      $(".formtastic.menu li#menu_"+key+"_input.required").append('<p class="inline-errors">'+value.join(", ")+'</p>');
    });
  }
});