node+express+mongodb,登陆代码备份二（+promise）（自用）

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//index.js改为：var express = require('express');var router = express.Router();var promise = require("promise");var mp = require("mongodb");//此处稳定版的node支持mongodb-promiseconsole.log('>>> a');mp.MongoClient.connect("mongodb://127.0.0.1:27017/test").then(function(db){    console.log('>>> b');    Promise.resolve(db.collection('users')).then(function(user) {        console.log('>>> c');        router.get('/', function(req, res) {            res.render('index', { title: 'index' });        });        /*login*/        router.get('/login', function(req, res) {            res.render('login', { title: 'login' });        });        /*logout*/        router.get('/logout', function(req, res) {            res.render('logout', { title: 'logout' });        });        /*hompage*/        router.post('/homepage', function(req, res) {            var query_doc = {userid: req.body.name, password: req.body.password};            console.log(query_doc);            user.findOne(query_doc).then(function(err, user){                if(user !== null){                    console.log(query_doc.userid + ": login success in " + new Date());                    res.render('homepage', { title: 'homepage' });                }else{                    console.log(query_doc.userid + ": login failed in " + new Date());                    res.redirect('/');                }            });        });    }, function(err) {        console.log('>>> d',err);    });}, function(err) {    console.log('>>> e',err);});module.exports = router;