Return certain fields with .populate() from Mongoose

I'm not completely clear on what you mean by "returning a field", but you can use a lean() query so that you can freely modify the output, then populate both fields and post-process the result to only keep the field you want:

.lean().populate('user', 'email.address facebook.address')  .exec(function (err, subscription){     if (subscription.user.email.address) {        delete subscription.user.facebook;    } else {        delete subscription.user.email;    }  });

If you only want a few specific fields to be returned for the populated documents, you can accomplish this by passing the field name syntax as the second argument to the populate method.

Model.findOne({ _id: 'bogus' }).populate('the_field_to_populate', 'name') // only return the Persons name...

See Mongoose populate field selection

Try to do this:

applicantListToExport: function (query, callback) {  this   .find(query).select({'advtId': 0})   .populate({      path: 'influId',      model: 'influencer',      select: { '_id': 1,'user':1},      populate: {        path: 'userid',        model: 'User'      }   }) .populate('campaignId',{'campaignTitle':1}) .exec(callback);}