Node.js, Express and Mysql. How is correct way - mysql

Question

What i'am trying to achieve is to make DB query inside closure. Return data and then send stuff to user. I understand that best practice is to use database pooling. Problem is that query is not sync.
Simplified code:
server.js
var express = require('express'),
app = express(),
server = require('http').createServer(app),
mysql = require('mysql');
app.set('DB:pool', mysql.createPool(process.env.DATABASE_URL));
var myClosure = require('./closure.js')(app));
app.get('/somepage', function(req, res) {
var data = myClosure.myquery();
res.send(data);
});
app.get('/anotherpage', function(req, res) {
var data = myClosure.myquery();
res.send(data);
});
app.listen(3000);
closure.js
function myClosure(app) {
var pool = app.get('DB:pool');
return {
myquery: function(inp) {
pool.getConnection(function(err, db) {
if (err) throw err;
db.query('SELECT * FROM table', function(err, rows, fields) {
if (err) throw err;
data = rows[0]
db.release();
});
});
return data;
}
};
}
module.exports = myClosure;
In examples i found all DB related stuff were made in route callback and response was sent in query callback. But way i'm trying to do it is not working as myquery returns undefined because sql query is not done there.
So what is correct way to handle querys ?

Answer 1

Make your query-function handle a callback too:
// server.js
app.get('/somepage', function(req, res) {
myClosure.myquery(function(err, data) {
// TODO: handle error...
res.send(data);
});
});
// closure.js
...
myquery: function(callback) {
pool.getConnection(function(err, db) {
if (err) return callback(err);
db.query('SELECT * FROM table', function(err, rows, fields) {
// release connection before we return anything, otherwise it
// won't be put back into the pool...
db.release();
if (err) return callback(err);
callback(null, rows[0]);
});
});
}
(I left out the inp argument because that didn't seem to be used)