Possible to populate two levels?

Question

Say I have collections/documents like below:

question collection:

{
   _id: ObjectId(\"0000\"),
   title: \"test question\",
   survey: ObjectId(\"1234\"         


        

Answer 1

You need to do it in two steps; first populating survey, and then populating survey.user using a separate call to Model.populate:

questions.findOne({_id: '0000'})
    .populate('survey')
    .exec(function(err, question) {
        questions.populate(
            question,
            { path: 'survey.user', model: 'User'},
            function(err, question) {...});
    });