无法从节点连接到 mongodb.js

Question

我正试图编写一段代码，使用'mongodb'库从node.js连接到mongodb数据库。

下面是一段代码，描述了我想要实现的目标:

var Db = require('mongodb').Db,
MongoClient = require('mongodb').MongoClient,
Server = require('mongodb').Server,
ReplSetServers = require('mongodb').ReplSetServers,
ObjectID = require('mongodb').ObjectID,
Binary = require('mongodb').Binary,
GridStore = require('mongodb').GridStore,
Grid = require('mongodb').Grid,
Code = require('mongodb').Code,
assert = require('assert'); 
var User = require('mongo-bcrypt-user');
// Set up the connection to the local db
var mongoclient = new MongoClient(new Server("localhost", 27017), {native_parser: true});
var db = mongoclient.db("test");
var coll = db.collection('users');

尝试运行文件时，我得到以下错误:

D:mongodb.js:15
var db = mongoclient.db("test");
                   ^
TypeError: undefined is not a function
at Object.<anonymous> (D:BackupsC Drive New Backuptempmongodb.js:15:24)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
at Module.require (module.js:365:17)
at require (module.js:384:17)
at Object.<anonymous> (D:BackupsC Drive New BackuptempMyWebAPI.js:8:20)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)

Answer 1

MongoClient没有db方法:http://mongodb.github.io/node-mongodb-native/2.0/api/MongoClient.html

它有connect(url, options, callback)方法，其中callback是connectCallback(error, db)函数，所以你的代码必须看起来像这样:

var mongoclient = new MongoClient('mongodb://localhost:27017',      
                                  {native_parser: true}, 
                                  function(error, db) {
                                    // use db here
                                  });

注意JavaScript中异步编程的概念。即回调和承诺