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