javascript - 如何使用onChange()函数进行排序？

Question

请检查我的plunk当我使用按钮时它工作正常，但我希望下拉菜单具有相同的功能。

请解释一下如何写onChange()或编辑 plunk

代码:html: <select ng-options="d for d in opt2" ng-model="varun" ng-change="onchange()">
<option value="">Select One</option>
</select>

js:

$scope.order = function(predicate, reverse) {
      $scope.friends = orderBy($scope.friends, predicate, reverse);
    };

    $scope.varun = $scope.opt2[0];
   $scope.onchange = function() {
alert($scope.varun);
if($scope.varun == age2 )
{
   $scope.friends = orderBy($scope.friends, 'age' , false);
}
else
{
  $scope.order('-date',true);
}
  }
  }

Answer 1

如果你查看控制台，它会显示

ReferenceError: age2 is not defined

你需要写在下面

if($scope.varun == 'age2' )

而不是

if($scope.varun == age2 )