backbone-rails-model-error.js

    errorHandler: function (model, response) {
      var result = $.parseJSON(response.responseText);

      _(result.errors).each(function (errors, attribute) {
        var inputWithError = $('#'+attribute),
            parentDiv = inputWithError.parent();

        parentDiv.addClass('error');
        _(errors).each(function (error) {
          $("<span class='help-inline'></span>").
            text(error).
            appendTo(parentDiv);
        });
      });