jquery.validate: accordion show when form in it is invalid by config `invalidHandler`

a.js

$form.validate({
  ignore: '.ignore',
  rules: rules,
  messages: messages,
  invalidHandler: function(event, validator) {
    // console.log(event, validator);
    var errorEl = validator.findLastActive() || validator.errorList.length && validator.errorList[0].element;
    if(errorEl)
      $(errorEl).closest('.accordion-body').collapse('show');
  },
  submitHandler: function(form) {
    _submitForm(form);
    return false;
  }
});