old_contents: 'use strict';
  
  /**
   * Module dependencies
   */
  import * as mongo from 'mongodb';
  import Favorite from '../models/favorite';
  import serialize from '../../serializers/post';
  
  /**
   * Get followers of a user
   *
   * @param {Object} params
   * @return {Promise<object>}
   */
  module.exports = (params) =>
  	new Promise(async (res, rej) =>
  {
  	// Init 'limit' parameter
  	let limit = params.limit;
  	if (limit !== undefined && limit !== null) {
  		limit = parseInt(limit, 10);
  
  		// 1 ~ 100 まで
  		if (!(1 <= limit && limit <= 100)) {
  			return rej('invalid limit range');
  		}
  	} else {
  		limit = 10;
  	}
  
  	// Init 'offset' parameter
  	let offset = params.offset;
  	if (offset !== undefined && offset !== null) {
  		offset = parseInt(offset, 10);
  	} else {
  		offset = 0;
  	}
  
  	// Init 'sort' parameter
  	let sort = params.sort || 'desc';
  
  	// Get favorites
  	const favorites = await Favorites
  		.find({
  			user: user._id
  		}, {}, {
  			limit: limit,
  			skip: offset,
  			sort: {
  				_id: sort == 'asc' ? 1 : -1
  			}
  		})
  		.toArray();
  
  	if (favorites.length === 0) {
  		return res([]);
  	}
  
  	// serialize
  	res(await Promise.all(favorites.map(async favorite =>
  		await serialize(favorite.post)
  	)));
  });
  
new_contents: 'use strict';
  
  /**
   * Module dependencies
   */
  import * as mongo from 'mongodb';
  import Favorite from '../../models/favorite';
  import serialize from '../../serializers/post';
  
  /**
   * Get followers of a user
   *
   * @param {Object} params
   * @return {Promise<object>}
   */
  module.exports = (params) =>
  	new Promise(async (res, rej) =>
  {
  	// Init 'limit' parameter
  	let limit = params.limit;
  	if (limit !== undefined && limit !== null) {
  		limit = parseInt(limit, 10);
  
  		// 1 ~ 100 まで
  		if (!(1 <= limit && limit <= 100)) {
  			return rej('invalid limit range');
  		}
  	} else {
  		limit = 10;
  	}
  
  	// Init 'offset' parameter
  	let offset = params.offset;
  	if (offset !== undefined && offset !== null) {
  		offset = parseInt(offset, 10);
  	} else {
  		offset = 0;
  	}
  
  	// Init 'sort' parameter
  	let sort = params.sort || 'desc';
  
  	// Get favorites
  	const favorites = await Favorites
  		.find({
  			user: user._id
  		}, {}, {
  			limit: limit,
  			skip: offset,
  			sort: {
  				_id: sort == 'asc' ? 1 : -1
  			}
  		})
  		.toArray();
  
  	if (favorites.length === 0) {
  		return res([]);
  	}
  
  	// serialize
  	res(await Promise.all(favorites.map(async favorite =>
  		await serialize(favorite.post)
  	)));
  });
  
subject: Fix bug