multiple async mongo request in nodejs

Question

multiple async mongo request in nodejs

How to write multiple queries in a row?

Like a

Space.findOne({ _id: id }, function(err, space) {
    User.findOne({ user_id: userid }, function(err, user) {
        res.json({ space: space, user: user});
    });
});

does not look good with more requests and logic

How is it done correctly?

I heard something about the promise, but I do not know.

Thanks

javascript
node.js
mongodb
asynchronous

Answer 1

When I've had a similar issue, I've used the async library.

async.parallel([
    function(callback){
       Space.findOne({ _id: id }, callback);
    },
    function(callback){
        User.findOne({ user_id: userid },callback);
    }
],
function(err, results){
    res.json({space:results[0],user:results[1]});
});

You can also use async.series if you want sequential execution.

Answer 2

@Benjamin's approach is correct. Mongoose also provides the populate method, which fetches multiple objects that are related to each other by their id. This also happens in parallel and is a special case of multiple queries. See http://mongoosejs.com/docs/populate.html for more examples.