angularjs已经选择的值不应该出现在来自json的另一个下拉列表中

<select ng-model="selectedValue" ng-options="option for option in availableOptions"></select>
<select ng-model="selectedValue2" ng-options="option for option in availableOptions2"></select>

app.controller('myController', function($scope) {
  $scope.availableOptions = ['Option 1', 'Option 2', 'Option 3'];
  $scope.availableOptions2 = ['Option 4', 'Option 5', 'Option 6'];

  $scope.selectedValue = $scope.availableOptions[0];
  $scope.selectedValue2 = $scope.availableOptions2[0];

  $scope.$watch('selectedValue', function(newValue) {
    // Remove selected value from available options
    var index = $scope.availableOptions2.indexOf(newValue);
    if (index !== -1) {
      $scope.availableOptions2.splice(index, 1);
    }
  });

  $scope.$watch('selectedValue2', function(newValue) {
    // Remove selected value from available options
    var index = $scope.availableOptions.indexOf(newValue);
    if (index !== -1) {
      $scope.availableOptions.splice(index, 1);
    }
  });
});

<div ng-controller="myController">
  <select ng-model="selectedValue" ng-options="option for option in availableOptions"></select>
  <select ng-model="selectedValue2" ng-options="option for option in availableOptions2"></select>
</div>