我遇到与选择未定义相同的问题。toLowerCase为了安全起见，对此进行了变通并添加了功能。

$('#' + specificInput).autocomplete({ 
  create: function () {
    $(this).data('ui-autocomplete')._renderItem = function (ul, item) {
      $(ul).addClass('for_' + specificInput); //usefull for multiple autocomplete fields
      return $('<li data-id = "' + item.id + '">' + item.value + '</li>').appendTo(ul); 
    };
  }, 
  change:
    function( event, ui ){
      var selfInput = $(this); //stores the input field
      if ( !ui.item ) { 
        var writtenItem = new RegExp("^" + $.ui.autocomplete.escapeRegex($(this).val().toLowerCase()) + "$", "i"), valid = false;

        $('ul.for_' + specificInput).children("li").each(function() {
          if($(this).text().toLowerCase().match(writtenItem)) {
            this.selected = valid = true;
            selfInput.val($(this).text()); // shows the item's name from the autocomplete
            selfInput.next('span').text('(Existing)');
            selfInput.data('id', $(this).data('id'));
            return false;
          }
        });

        if (!valid) { 
          selfInput.next('span').text('(New)');
          selfInput.data('id', -1); 
        }
    }
}