json - angularjs count duplicate values in array of objects -

i'm working angularjs. have array of objects this:

 $scope.documents =    [         {             "id": "221",             "activate": "t"         },         {             "id": "1",             "activate": "t"                 },         {             "id": "2",             "activate": "t"                 },         {             "id": "221",             "activate": "t"                 },         {             "id": "5",             "activate": "t"                 },         {             "id": "221",             "activate": "t"                 },         {             "id": "221",             "activate": "t"                 },         {             "id": "7",             "activate": "t"                 },         {             "id": "8",             "activate": "t"                 },         {             "id": "9",             "activate": "t"                 },         {             "id": "221",             "activate": "t"                 }      ] 

i need angularjs function count number of repeated values in array of objects.

something this:

  $scope.count = function(param) {      angular.foreach($scope.preguntas, function(value, key) {         if (value.id == param){         ........         ........         }     });    }; 

but i'm not sure how can do.

i hope result this:

count(221); 5 

any of have suggestions please?

just increment count variable in if statement , return it.

$scope.count = function(param) {   var count = 0;    $scope.documents.foreach(function(document) {       if(document.id === param.tostring() {         count++;       }   });    return count; }; 

and markup:

<div>{{count(221)}}</div>