Cannot call method 'collection' of null

[dileephell]

var Db = require('mongodb').Db; var Server = require('mongodb').Server; new Db('db-login', new Server('localhost', '27017')); var db = new Db('db-login', new Server('localhost', '27017', { auto_reconnect: true },{safe:false}));

db.open(function (err, db) { if (err) { console.log(err + ' db open error') } db.authenticate('jones', 'jones', function (err, result) { if (err) { console.log(err + ' auth error'); } else{ console.log('Authenticated..'); } }); });

exports.getlogin=function getlogin(uid,pwd,callback){ Db.connect('mongodb://admin:markingof@localhost:27017/db-login', function (err, db) { db.collection('maccount_logins', function(err, collection) {

collection.find({"user.userid":uid,"user.pwd":pwd,"user.status":"true"},{"acc_type":"","acc_prefix":"","db_name":"","user.role":"","_id":0}).toArray(function(err, items) {
    if(err){console.log(err+'i am stuck');}
    else{

            callback("",items);
    }

 });

}); }); };

[Minstel]

@dileephell Issue is not clear.