gistfile1.js

// Preview button
$(document).on('click', '#btn-preview', function (event) {
  $.when(App._doFormAutosave()).done(function() {
    // here I want the event to not be prevented
  });
  event.preventDefault();
});

// Preview button
$(document).on('click', '#btn-preview', function (event) {
  var self = this;
  $.when(App._doFormAutosave()).done(function() {
    self.dispatchEvent(event);
  });
  event.preventDefault();
});

// Preview button
$('#btn-preview').on('click', function (event) {
  var $btn = $(this);
  if ($btn.data('follow') === undefined) {
    $.when(App._doFormAutosave($formBrandEdit)).done(function(response) {
      $btn
        .data('follow', true)
        .attr('href', window.globalConfig.baseUrl + 'marca/' + response.brand.url)
        .attr('target', '_blank')
        .trigger(event);
    });
    event.preventDefault();
  }
  else {
    $btn.removeData('follow');
  }
});