angular过滤器怎么进行排序？

 1 <div id="box"> 2             <!--第一个下拉框--> 3             <select ng-model="a"> 4                 <option value="age">按照年龄排序</option> 5                 <option value="code">按照编码排序</option> 6                 <option value="name">按照姓名排序</option> 7             </select> 8             <!--升序还是降序--> 9             <select ng-model="b">10                 <option value="">升序</option>11                 <option value="-">降序</option>12             </select>13             <!--一个搜索框-->14             <input type="text" placeholder="请输入要搜索的内容" ng-model="c"/>15         </div>16         <!--渲染的数据-->17         <div id="wrap">18             <table>19                 <tr>20                     <th>编码</th>21                     <th>姓名</th>22                     <th>年龄</th>23                 </tr>24                 <tr ng-repeat="item in data|filter:c|orderBy:b+a">25                     <td>{{item.code}}</td>26                     <td>{{item.name}}</td>27                     <td>{{item.age}}</td>28                 </tr>29             </table>30         </div>31

1 <script>2             var app = angular.module("mk",[]);3             app.controller("test",function($scope,$http){4                 $http.get('json/index.json').success(function(data){5                         $scope.data = eval(data);6                         $scope.a = "code";7                 })8             })9         </script>