只要SSCityList有改变就会自动选择第一项
<select id="SSType" name="SSType" class="form-control" isvalid="yes" checkexpression="NotNull"> <option value="0">请选择</option> <option v-for="(item,index) in SSCityList" :key="index" :value="item.CityId" :selected="index==0">{{item.Name}}</option> </select>