MongoDB 2.6 + NodeJS can't iterate cursor

I really can't figure out what's wrong, please help.

MongoDB version 2.6.7

I can insert without any problem, however Find function preforms very wired, see below codes.

Code A works very well.

var mongoClient = require("mongodb").MongoClient;
var express = require("express");
var app = express(); 

mongoClient.connect("mongodb://localhost:27017/feeding", function(err,database){
    if(!err){
        db.collection('test').find({}).toArray(function(err, users){
            console.log(users);
        });
        app.listen(8888, function(){
            console.log("Server Started");
        });
    }else{
        console.dir(err);
    }
});

Below B code throws 'TypeError: undefined is not a function' at line 25

var mongoClient = require("mongodb").MongoClient;
var express = require("express");
var app = express(); 

mongoClient.connect("mongodb://localhost:27017/feeding", function(err,database){
    if(!err){
        var cursor = db.collection('test').find({});
        while (cursor.hasNext()) { //line 25
            console.log("printed");
        }
        app.listen(8888, function(){
            console.log("Server Started");
        });
    }else{
        console.dir(err);
    }
});

I believe it says hasNext() is not a function, but refer to MongoDB document http://ift.tt/1LkX1sH, seems the code doesn't have any problem, have spent few hours on the issue. anybody can give me a suggestion?