Select a random document with Mongoose

findRandom.js

function findRandom(limit) {
  return Promise(function(resolve, reject) {
    Model.count({}, function(err, count) {
      var skip = _.random(0, count - limit);
      Model.find().skip(skip).limit(limit).exec(function(err, docs) {
        if (err)
          return reject(err);
        resolve(docs);
      });
    });
  });
}