MongoDB Node.JS Driver 1.4.9 documentation

db.open(function(err, db) {

摘自

MongoDB Node.JS Driver 1.4.9 documentation 

open

Initialize the database connection.
open(callback)

Arguments:	callback (function) – this will be called after executing this method. The first parameter will contain the Error object if an error occurred, or null otherwise. While the second parameter will contain the index information or null if an error occurred.
Returns:	null

Examples

An example of a simple single server db connection

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,
BSON = require('mongodb').pure().BSON,
assert = require('assert');

var db = new Db('test', new Server('localhost', 27017));
// Establish connection to db
db.open(function(err, db) {
assert.equal(null, err);

db.on('close', test.done.bind(test));
db.close();
});