anchor.diff:  
     dropDown.hide();
   
  -  cancel.click(function() {
  +  cancel.click(() => {
       dropDown.slideUp('slow', function() {
         inputId.show()
                .prop('disabled', false)
  
positive.code:             cancel.hide();
            }
            inputId.prop('disabled', true);
            inputId.slideUp('fast', function() {
              dropDown.slideDown('slow');
            });
          }
  
negative.code:   const ok = $('button#ok');
    const cancel = $('button#cancel');
  
    const autoDropDown = () => {
      const id = inputId.val();
      if (id.length >= 6) {
        $.getJSON('/id_join/drop_down', { id: id }, (dojo) => {
  