How do I send multiple queries from one endpoint with Express?

Question

I am trying to query my database several times and construct an object which stores every response from my database in a field. Here is my code:

router.post(\'/s         


        

Answer 1

You can do it with Promises

router.post('/search', (req, res) => {
    var collection = db.get().collection('styles');
    // Create promise for "make.name" query
    let firstQuery = new Promise((resolve, reject) => {
        collection.distinct('make.name', (err, docs) => {
            if (!err) {
                resolve(docs);
            } else {
                reject(err);
            }
        });
    });
    // Create promise for "model" query
    let secondQuery = new Promise((resolve, reject) => {
        collection.distinct('model', (function (err, docs) {
            if (!err) {
                resolve(docs);
            } else {
                reject(err);
            }
        }))
    })
    // Run both queries at the same time and handle both resolve results or first reject
    Promise.all([firstQuery, secondQuery])
        .then((results) => {
            res.send({ "make.name": results[0], "model": results[1] });
        })
        .catch((err) => {
            // Catch error 
            res.send({});
        });
});

Also you can use destructuring in callback functions like that:

Promise.all([firstQuery, secondQuery])
    .then(([makeName, model]) => res.send({ "make.name": makeName, model }))

UPD: If you have a bunch of collection to request you can create an array of collections name, map it to promise requests and handle with Promise.all, for example

let collections = ["firstCollection", "secondCollection", "nCollection"];
let promises = collections.map((collectionName) => {
    return new Promise((resolve, reject) => {
        collection.distinct(collectionName, (err, docs) => {
            if (!err) {
                resolve(docs)
            } else {
                reject(err);
            }
        });
    })
});
Promise.all(promises)
    .then(results => {
        // Do what you want to do
    })
    .catch(error => {
        // or catch 
    });