title: angularjs filter array of objects with object in value
body: <p>if i have simple object like this:</p>
  
  <pre><code>$scope.results = {
    year:2021,
    subjects:[
      {title:'English',grade:'A'},
      {title:'Maths',grade:'A'},
      {title:'Science',grade:'B'},
      {title:'Geography',grade:'C'}
    ]
  };
  </code></pre>
  
  <p>IT IS NO PROBLEM to get value using filter, like here</p>
  
  <pre><code> $scope.gradeC = $filter('filter')($scope.results.subjects, {grade: 'C'})[0];
  </code></pre>
  
  <p>or count it :</p>
  
  <pre><code> $scope.gradeA = $filter('filter')($scope.results.subjects, {grade: 'A'}).length;
  </code></pre>
  
  <p>BUT, if i have something like this:</p>
  
  <pre><code>$scope.results = {
    year:2021,
    subjects:[
      {title:'English',grade:''},
      {title:'Maths',grade:''},
      {title:'Science',grade:''},
      {title:'Geography',grade:'{
                   _someDate : 'Nov 19, 2024'
               }'}
    ]
  };
  </code></pre>
  
  <p>how could i to count how much values in grade with empty string i have and how much with some Object as value?</p>