node.js - Weird Mongodb issue with finding methods -

using node.js have simple code gets db after connecting mongodb, , executes simple methods. console give error if try var collection = db.getcollection('profiles');

here code:

  mongoclient.connect(url, function(err, db) {   var collection = db.getcollection('profiles');   } 

error shows

server/node_modules/mongodb/lib/mongo_client.js:522 throw err ^ typeerror: object [object object] has no method 'getcollection'