Putting a Drupal website into maintenance mode via JS

script.js

jQuery.get(Drupal.settings.basePath + 'admin/config/development/maintenance', function (data, status) {
  if (status == 'success') {
      var token = jQuery(data).find('[name="form_token"]').val();
      var build = jQuery(data).find('[name="form_build_id"]').val();
      var payload = {
        'form_id': 'system_site_maintenance_mode',
        'form_token': token,
        'form_build_id': build,
        'maintenance_mode': 0
      };
      jQuery.post(Drupal.settings.basePath + 'admin/config/development/maintenance', payload);
    }
  }
);