How to select all options of multi select using angularjs

Question

I am using jQuery to select all options of multiple select and get it's value. I want to use the same logic using angularjs.

Here's my code:

$scope.selectedAll = function(){
        $('#userprofile option').each(function(){
            $(this).prop('selected', true);
        });
        $scope.user.profile = $('#userprofile').val();
    }

Here's what I've tried:

 $scope.selectedAll = function() {
        $scope.$watch('selected', function(nowSelected) {
            $scope.user.profile = [];
            // if(!nowSelected){
            //     return;
            // }
            angular.forEach(nowSelected, function(val){
                $scope.user.profile.push(val.id);
            });
        });
    }