envia formulário ruby on rails via ajax e exibe erros automaticamente com script

_form.html.erb

<%= form_for(@model, remote: true, html: {role: :form, 'data-model' => 'MODEL_NAME', class: 'send_ajax'}) do |f| %>
  <% if @model.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@model.errors.count, "error") %> prohibited this tip from being saved:</h2>

      <ul>
      <% @model.errors.full_messages.each do |message| %>
        <li><%= message %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="status" style="display:none;">Success message!</div>
  <div class="row">
    <div class="col-sm-12">
      <%= f.text_area :explanation, rows: 5, placeholder: "How are you?" %>
      <span class="help-block"></span>
    </div>
  </div>

  <div class="row">
    <div class="col-sm-6">
      <%= f.text_field :name, placeholder: "Your name" %>
      <span class="help-block"></span>
    </div>
    <div class="col-sm-6">
      <%= f.text_field :email, placeholder: "Your email" %>
      <span class="help-block"></span>
    </div>
  </div>


  <div class="row">
    <div class="col-sm-12 text-center">
      <%= f.submit "Submit" %>
    </div>
  </div>
<% end %>

forms.js

$(document).ready(function(){

  $(document).bind('ajaxError', 'form.send_ajax', function(event, jqxhr, settings, exception){
    $(event.data).render_form_errors( $.parseJSON(jqxhr.responseText) );
  })
  .bind('ajaxSuccess', 'form.send_ajax', function(event, jqxhr, settings, exception){
    $(event.data).clear_form();
    $(event.data).success()
  });

});

(function($) {

  $.fn.clear_form = function(){

    // clear form input elements
    this.find('input[type="text"]').val('');
    this.find('textarea').val('');

    // clear error state
    this.clear_previous_errors();
  };

  $.fn.render_form_errors = function(errors){
    // $form = this;
    this.clear_previous_errors();
    model = this.data('model');
    // show error messages in input form-group help-block
    $.each(errors, function(field, messages){
      $input = $('[name="' + model + '[' + field + ']"]');
      $input.closest('div').addClass('has-error').find('.help-block').html( messages.join(' & ') );
    });

  };

  $.fn.clear_previous_errors = function(){
      $('.has-error', this).each(function(){
      $('.help-block', $(this)).html('');
      $(this).removeClass('has-error');
    });
  }

  $.fn.success = function() {
    $('.status', this).show();
  }

}(jQuery));