Looking for suggestion using Promise

[Ashutosh Das]

I am using Mongoose with Bluebird library . Here is my code:

router.route('/:name')
        .get(function (req, res) {
                var values = [];
                 Tag.findOneAsync({'name': req.params.name}, {urlId: 1, _id: 0}).then(function (data) {
                    data['urlId'].forEach(function (urlId) {
                        Urls.findByIdAsync(urlId).then(function (result) {
                            values.push(result);
                        }).catch(function (err) {
                            res.status(500).send(err);
                        });
                    });
                }).catch(function (err) {
                    res.status(500).send(err);
                });

                res.send(values);
     });

Currently I am gettings empty 'values' array . My question is, how to organize this code , so that I can get response after 'values.push()' operation ?

[Aria Stewart]

You're making an empty array, starting the find, then sending the array, then later, filling the array.

You'd move the res.send into the promise chain -- let me suggest a rewrite here:

router.route('/:name').get(function (req, res) {

Tag.findOneAsync({'name': req.params.name}, {urlId: 1, _id: 0}).then(function (data) {

         return Promise.all(data['urlId'].map(function (urlId) {
                        return Urls.findByIdAsync(urlId)
})
}).then(function (values) {
res.send(values);
}, function (err) {
                res.status(500).send(err);
});
});

It's nice to think of 'then' as a singular 'map' -- take this value, and transform it into that value (or a promise of a value or values)

Promise.all resolves a whole array of promises like that set of results of findByIdAsync.

Aria