angularjs watch list. avoid duplicated watching

angularjs_watch_list

$scope.watcher_switches = [];

$scope.add_status_watcher = function () {
    //stop watching
    angular.forEach($scope.watcher_switches, function (value) {
        value();
    });
    //bind new watchers
    var new_watchers = [];

    for(var key in $scope.rule_sets) {
        if($scope.rule_sets.hasOwnProperty(key)) {
            var watcher_switch = $scope.$watch("rule_sets['" + key + "']", function(newValue, oldValue) {
                if (newValue !== oldValue &&
                    newValue.status != oldValue.status) {
                    if (newValue.status == 'ON') {
                        $http.put('/api/rule_set/enable?id=' + newValue.id);
                    } else {
                        $http.put('/api/rule_set/disable?id=' + newValue.id);
                    }
                }
            },true);
            new_watchers.push(watcher_switch);
        }
    }
    //replace previous watcher array
    $scope.watcher_switches = new_watchers;
};