feed endpoint

//...

// feed from authors user is following
router.get('/feed', auth.required, function(req, res, next){
  // configure the query params
  var limit = 20;
  var offset = 0;

  if(typeof req.query.limit !== 'undefined'){
    limit = req.query.limit;
  }

  if(typeof req.query.offset !== 'undefined'){
    offset = req.query.offset;
  }

  // grab user from mongo
  User.findById(req.payload.id).then(function(user){
    if (!user) { return res.sendStatus(401); }

    // find the paginated list of articles for authors we're following
    Promise.all([
      Article.find({ author: {$in: user.following}})
        .limit(Number(limit))
        .skip(Number(offset))
        .populate('author')
        .exec(),
      Article.count({ author: {$in: user.following}})
    ]).then(function(results){
      // return list of article JSON's
      var articles = results[0];
      var articlesCount = results[1];

      return res.json({
        articles: articles.map(function(article){
          return article.toJSONFor(user);
        }),
        articlesCount: articlesCount
      });
    }).catch(next);
  });
});

//...