Node.js / Mongodb insert callback return undefined

Er is ops object in records die ingevoegde doc/docs bevat.

Probeer:

collectionUsers.insert({'name':'john'},function(err,records){
   // You can explore more here
   console.log("record contents",JSON.stringify(records,null,4));
   // Desired output
   console.log("Id of new document added =  " + records.ops[0]._id);
});