How to save datetime as BSON Date using Node driver?

Question

I'm using the Node MongoDB driver to collect analytics for my website and send them to MongoLab. How does one insert the current datetime into a document so it can later be used to do aggregation in Mongo?

To be clear, here is the code:

var query = {};
query['date_time'] = new Date();
Db.connect(mongoUri, function (err, db) {
        if (!err) {
            db.collection(analyticsCollection, function (err, coll) {
                if (!err) {
                    coll.save(query, {safe:true}, function (err, result) {
                        db.close();
                        res.send(200,result);
                        //console.log(result);
                    });
                } else {
                    res.json(503,{errno:503,msg:'error: collection does not exist.'});
                }
            });
        } else {
            res.json(503,{errno:503,msg:'error: database does not exist.'});
        }
    });

The MongoDB documentation describes how to create a BSON date in the mongo shell, but not in the Node driver and I can't find it in the Node driver docs either.

Answer 1

I found a way to do what I wanted to do. This seems kind of klugey to me, so if anyone can find a better way, please let me know. My solution uses the underscore.js library:

var _ = require('underscore');
vary query = {}
query['foo'] = 'bar'

Db.connect(mongoUri, function (err, db) {
        if (!err) {
            db.collection(analyticsCollection, function (err, coll) {
                if (!err) {
                    coll.save(_.extend(query,{"datetime":new Date()}), {safe:true}, function (err, result) {
                        db.close();
                        res.send(200,result);
                        //console.log(result);
                    });
                } else {
                    res.json(503,{errno:503,msg:'error: collection does not exist.'});
                }
            });
        } else {
            res.json(503,{errno:503,msg:'error: database does not exist.'});
        }
    });

Now I can do the aggregation (without needing to use the $project operator):

> db.analytics.aggregate([{$group:{_id:{day:{$dayOfMonth:"$datetime"}}}}])
{ "result" : [ { "_id" : { "day" : 15 } } ], "ok" : 1 }

Hope this helps someone.