easyui combobox下拉列表的多选值

<input id="cc" class="easyui-combobox" value=""  data-options="
url:'xxxxxx',
method:'get',
valueField:'id',
textField:'groupName',
multiple:true,
panelHeight:'auto',
loadFilter:function(data){
return data.data.rows;
}"
/>
<a id="btnGet" class="easyui-linkbutton" data-options="iconCls:'icon-add'">获取已选项集合值</a>

$("#btnGet").click(function () {
alert( $('#cc').combobox('getValues'));
});