unshift_cast.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_unshiftcast';
console.log('dbname: %s', dbname);
mongoose.connect('localhost', dbname);
mongoose.connection.on('error', function () {
  console.error('connection error', arguments);
});

var comment = new Schema({ comment: { type: String}, date: { type: Date, default: Date.now }});
var Comment = mongoose.model('Comment', comment);

var schema = new Schema({
    name: String
  , comments: [comment]
});

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

mongoose.connection.on('open', function () {
  var a = new A({ name: 'unshiftcast' });

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

    A.findById(a, function (err, doc) {
      console.error('found', doc);

      var newComment = new Comment({ comment:'hi' });
      doc.comments.unshift(newComment);

      // or use
      //doc.comments.unshift({ comment: 'hello' });

      doc.save(function () {
        if (err) return done(err);
        A.findById(a, function (err, doc) {
          if (err) return done(err);
          console.log('after update', doc);
          done(err);
        })
      })
    });
  })
});

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