初始化 db.js

const mongoose = require('mongoose');
const Config = require('../../config');
mongoose.Promise = require('bluebird');

user.js

const User = require('./db/mongodb').UserModel;

exports.findById = function(username){
  return User.findOne({username:username}).exec();
};

userService.js

exports.getUser = function(username,password){`
  return User.findById(username).then((userInfo) => {
   return Promise.resolve(userInfo);
 
    }else{
      return Promise.reject('No Such User');
    }

这样明显比回调的写法简单清晰多了