ajax_form.js

$('form').submit(function() {
    var valuesToSubmit = $(this).serialize();
    $.ajax({
        type: "POST",
        url: $(this).attr('action'), //sumbits it to the given url of the form
        data: valuesToSubmit,
        dataType: "JSON" // you want a difference between normal and ajax-calls, and json is standard
    }).success(function(json){
        //act on result.
alert('Hello world');
    });
    return false; // prevents normal behaviour
alert('False');
});

$('#form').on('ajax:success', function(event, data, status, xhr) {
  alert('hello world');
});



$(document).ready(function(){

  $(document).bind('ajaxError', 'form', function(event, jqxhr, settings, exception){

    // note: jqxhr.responseJSON undefined, parsing responseText instead
    $(event.data).render_form_errors( $.parseJSON(jqxhr.responseText) );

  });

});

(function($) {

  $.fn.modal_success = function(){
    // close modal
    this.modal('hide');
  alert('hello world');
    // clear form input elements
    // todo/note: handle textarea, select, etc
    this.find('form input[type="text"]').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 = $('input[name="' + model + '[' + field + ']"]');
      $input.closest('.form-group').addClass('has-error').find('.help-block').html( messages.join(' & ') );
    });

  };

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

}(jQuery));