using the $elemMatch projection with mongoose

mongoose_with_mongo2-2_elemMatch_projection.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var assert = require('assert')

console.log('\n===========');
console.log('    mongoose version: %s', mongoose.version);
console.log('========\n\n');

var dbname = 'testing_1085';
mongoose.connect('localhost', dbname);
mongoose.connection.on('error', function () {
  console.error('connection error', arguments);
});

var schema = new Schema({
    items: [Number]
});

var A = mongoose.model('A', schema);

mongoose.connection.on('open', function () {
  var a = new A({ items: [1,3,5,7,9] });

  a.save(function (err, a) {
    if (err) return done(err);

    //A.findOne({ _id: a._id, items: { $elemMatch: {$in: [1,5,9] }}}).exec(function (err, docs) {
    A.findOne({ _id: a._id }).select({ items: { $elemMatch: {$in: [1,5,9] }}}).exec(function (err, doc) {
      console.log(doc); // { _id: 50478c35889a450000000001, items: [ 5 ] }
      done(err);
    });
  })
});

function done (err) {
  if (err) console.error(err.stack);
  mongoose.connection.db.dropDatabase(function () {
    mongoose.connection.close();
  });
}