code: function(ev) {
              var regex = new RegExp(searchBox.value, 'i'),
                  targets = optionsList.querySelectorAll('li');
  
              for (var i=0; i<targets.length; i++) {
                  var target = targets[i];
  
                  // With multiple active options are never shown in the options list, with single
                  // we show both the active/inactive options with the active highlighted
                  if(multiple && target.classList.contains('active'))
                      continue;
  
                  if(!target.textContent.match(regex)) {
                      target.style.display = 'none';
                  } else {
                      target.style.display = 'block';
                  }
              };
  
              searchBox.style.width = ((searchBox.value.length * selected.textWidth) + 25) + 'px';
              moveOptionList();
          }
docs: Filter options list by searchbox results