我有一个关于如何打开mongodb连接一次的问题,然后在user.js中的集合名称用户和comment.js中的集合名称帖子中使用它

我想在db.js中打开db连接,然后为用户和帖子集合插入/保存数据

目前代码,我的db.js

var Db = require('mongodb').Db,Connection = require('mongodb').Connection,Server = require('mongodb').Server;
module.exports = new Db(
    'blog',new Server('localhost',Connection.DEFAULT_PORT,{auto_reconnect: true})
);

我在user.js中使用了db.js,如下所示

var mongodb = require('./db');

function User(user){
  this.name = user.name;
  this.password = user.password;
  this.email = user.email;
};

module.exports = User;

User.prototype.save = function(callback) {//save user information
  //document to save in db
  var user = {
      name: this.name,password: this.password,email: this.email
  };
  mongodb.close();
  //open mongodb database
  mongodb.open(function(err,db){
    if(err){
      return callback(err);
    }
    //read users collection
    db.collection('users',function(err,collection){
      if(err){
        mongodb.close();
        return callback(err);
      }
      //insert data into users collections
      collection.insert(user,{safe: true},user){
        mongodb.close();
        callback(err,user);//success return inserted user information
      });
    });
  });
};

和comment.js

var mongodb = require('./db');

function Comment(name,day,title,comment) {
  this.name = name;
  this.day = day;
  this.title = title;
  this.comment = comment;
}

module.exports = Comment;

Comment.prototype.save = function(callback) {
  var name = this.name,day = this.day,title = this.title,comment = this.comment;
  mongodb.open(function (err,db) {
    if (err) {
      return callback(err);
    }
    db.collection('posts',function (err,collection) {
      if (err) {
        mongodb.close();
        return callback(err);
      }
      //depend on name time and title add comment
      collection.findAndModify({"name":name,"time.day":day,"title":title},[ ['time',-1] ],{$push:{"comments":comment}},{new: true},comment) {
          mongodb.close();
          callback(null);
      });   
    });
  });
};