Global objects with Node.js + Express

Question

I'm studying Node.js + Express, coding a basic login example. My /login route is set inside the routes/login.js file:

var express = require('express');
var router = express.Router();

var mysql = require('mysql');
var connectionpool = mysql.createPool({
    host     : 'localhost',
    user     : 'user',
    password : 'pass',
    database : 'database'
});

router.post('/', function(req,res){ 
    connectionpool.getConnection(function(err, connection) {
        if (err) {
            console.error('CONNECTION error: ',err);
            res.statusCode = 503;
              res.send({
                result: 'error',
                err:    err.code
            });
        } else {
            // Do something
        }
    });
});

module.exports = router;

I was wondering: how can I make the mysql or the connectionpool visible in the entire application? I don't want to redeclare them on each route file I'll create. I'm looking something like an include or require method.

Any idea?

Put that in a separate Node.js module and require it in all the files? — thefourtheye
– thefourtheye, Commented Oct 24, 2014 at 16:49

Evan Shortiss · Accepted Answer · 2018-07-12 19:18:13Z

6

Create a separate module to act as an interface to retrieving SQL connections like so:

    var mysql = require('mysql');
    var connectionpool = mysql.createPool({
      host     : 'localhost',
      user     : 'user',
      password : 'pass',
      database : 'database'
    });

    exports.getConnection = function (callback) {
      connectionpool.getConnection(callback);
    };

Then in another file:

    var connections = require('./connections');

        connections.getConnection(function (err, c) { 
    // Use c as a connection 
     c.query("select * from table limit 10 ",function(err,rows){
    //this is important release part 
                c.release();
                if(!err) {
                    console.log(rows);
                }           
            });

});

edited Jul 12, 2018 at 19:18

answered Oct 24, 2014 at 17:15

Evan Shortiss

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