list articles

//...

// endpoint to list all articles
router.get('/', auth.optional, function(req, res, next) {
  // set query, limit, offset params for filtering/pagination.
  var query = {};
  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;
  }

  // return promise for [articles matching query, count, user]
  return Promise.all([
    Article.find(query)
      .limit(Number(limit))
      .skip(Number(offset))
      .sort({createdAt: 'desc'})
      .populate('author')
      .exec(),
    Article.count(query).exec(),
    req.payload ? User.findById(req.payload.id) : null,
  ]).then(function(results){
    var articles = results[0];
    var articlesCount = results[1];
    var user = results[2];

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

//...