code: function fromJson(collection, collectionPath, next) {
  
    var docsBulk = [];
    var docs = fs.readdirSync(collectionPath);
    var last = ~~docs.length, counter = 0;
    if (last === 0) {
      return next(null);
    }
  
    docs.forEach(function(docName) {
  
      var doc, data;
      try {
        data = fs.readFileSync(collectionPath + docName);
      } catch (err) {
        return last === ++counter ? next(null) : null;
      }
      try {
        doc = JSON.parse(data);
      } catch (err) {
        return last === ++counter ? next(err) : error(err);
      }
  
      docsBulk.push({
        insertOne: {
          document: doc
        }
      });
  
      return last === ++counter ? collection.bulkWrite(docsBulk, next) : null;
    });
  }
docs: JSON parser
  
  @function fromJson
  @param {Object} collection - collection model
  @param {String} collectionPath - path of collection
  @param {Function} next - callback