According to the documentation (http://mongodb.github.io/node-mongodb-native/2.0/api/Collection.html#deleteOne) deleteOne callback returns
Collection~writeOpCallback

This is what I get after a successful delete.

It doesn't correspond to the description of the result Object (WriteOpResult) as stated in the doc.

I suppose "n" is the number of deleted documents ? Is "ok" always at 1 , otherwise we have an error object instead ?
what is "electionId" and lastOp ?

Thanks