Semantic UI 使用回调函数

<div class="ui dropdown item" id="region">
              <div class="text">区域</div>
              <i class="dropdown icon"></i>
              <div class="menu">
                  <div class="item" data-value="1">荆州区</div>
                  <div class="item" data-value="2">沙市区</div>
                  <div class="item" data-value="3">开发区</div>
                  
              </div>
           </div>

$("#region").dropdown({
        onChange:function(a,b){
            alert(a+"="+b);
        }
    });