angularJS ng-model无法获取WdatePicker清空之后的值

Question

如题：angularJS ng-model无法获取WdatePicker清空之后的值

<input id="startDate" type="text" ng-model="startDate" readonly="readonly" onclick="WdatePicker({dateFmt: 'yyyy-MM-dd HH:mm:ss',onpicked: function(){$(this).trigger('change')}})" class="form-control empty" />

 console.log($("#startDate").val());//日历控件清空后显示""
 console.log($scope.startDate);//日历控件清空后值未变化