angularjs promise inside a loop in factory method trouble

Question

I have a factory which contains getFeed() method with a loop inside

getFeed: function(offset){
      return vk.call('wall.get', {owner_id: owner_id, offset: offset, count: count, v: version}).then(function(res){
        console.log(res);
        items = res.data.response.items;
        for(var i = 0; i < items.length; i++){
          isLiked(items[i].id).then(function(ress){
            if(ress.data.response.liked == true){
              console.log(items[i]);
            }
          });
        }
        return items;
      }, function(err){
        console.log('cant call');
      });
 },

And console.log shows me undefined, isLiked() working normally, i think the problem is something with async, but i don't know how to solve it