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<!DOCTYPE html>
<html ng-app="ngMap">

<head>
  <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
  <script src="https://maps.google.com/maps/api/js?libraries=placeses,visualization,drawing,geometry,places"></script>
  <script src="https://code.angularjs.org/1.3.15/angular.js"></script>
  <script src="https://rawgit.com/allenhwkim/angularjs-google-maps/master/build/scripts/ng-map.js"></script>
  <script>
    angular.module('ngMap').controller('MyCtrl', function(NgMap, $scope) {
      var vm = this;

      vm.positions = [{
        pos: [40.71, -74.15]
      }, {
        pos: [40.72, -74.20]
      }, {
        pos: [40.73, -74.18]
      }, {
        pos: [40.77, -74.19]
      }, {
        pos: [40.75, -74.17]
      }, {
        pos: [40.76, -74.16]
      }, {
        pos: [40.74, -74.20]
      }];
      
      vm.positionsWithinBounds = angular.copy(vm.positions);

      var analyzeViewableMarkers = function(map) {
        var ne = map.getBounds().getNorthEast();
        var sw = map.getBounds().getSouthWest();

        var latBounds = {
          top: ne.lat(),
          bottom: sw.lat()
        };

        var lonBounds = {
          left: sw.lng(),
          right: ne.lng()
        };

        vm.positionsWithinBounds = angular.copy(
          vm.positions.filter(function(pos) {
            var liesWithinLatBounds = latBounds.top >= pos.pos[0] && latBounds.bottom <= pos.pos[0];
            var liesWithinLonBounds = lonBounds.left <= pos.pos[1] && lonBounds.right >= pos.pos[1];

            return liesWithinLatBounds && liesWithinLonBounds;
          })
        );
        
        // for some reason the $digest cycle doesn't catch changes to vm.viewablePositions
        // trigger it manually
        $scope.$apply();
      };

      NgMap.getMap().then(function(map) {
        vm.map = map;
        google.maps.event.addListener(map, 'bounds_changed', function() {
          analyzeViewableMarkers(map);
        });
      });
    });
  </script>
</head>

<body>
  <div ng-controller="MyCtrl as vm">
    <ng-map zoom="11" center="[40.74, -74.18]" trigger-resize="true">
      <marker ng-repeat="p in vm.positions" position="{{p.pos}}" title="pos: {{p.pos}}"></marker>
    </ng-map>
    <div>
      <div ng-repeat="p in vm.positionsWithinBounds">{{p.pos}}</div>
    </div>
  </div>
</body>

</html>