Deploying ReactJS app with NodeJS backend (using express) for server/database on heroku

const express = require('express');
const bodyParser = require('body-parser');
const mysql      = require('mysql');
var url = require('url');
const path = require ('path')
// données de ma bd
const connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : '',
  database : 'l3ad2'
});


const app = express();

app.use(function(req, res, next) {
res.header("Access-Control-Allow-Origin", "*");
res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
next();
});


if (process.env.NODE_ENV === 'production') {
   app.use(express.static('client/build'));
   app.get('*', (req, res) => {
     res.sendFile(path.resolve(__dirname, 'client', 'build', 'index.html'));
   });
}

//crée une connection a ma bd
connection.connect();
// création de la database
connection.query("CREATE DATABASE IF NOT EXISTS bd_l3ad", function (err, result) {
  if (err) throw err;

});
//création de la table LignesCollection
 var sql1= "CREATE TABLE IF NOT EXISTS LignesCollection ( numero INTEGER UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY , collection VARCHAR(30), objet VARCHAR(30), descriptionObjet VARCHAR(250) , Avendre  VARCHAR(30) DEFAULT 'no' , prix VARCHAR(30), urlimage VARCHAR(250) )";
 connection.query(sql1, function (err, result) {
   if (err) throw err;
 });


// envoi des données de la table collection dans un serveur http://localhost:3004//getCollections
app.get('/getCollections', function (req, res) {


    connection.query('SELECT nom FROM collections', function (error, results) {
      if (error) throw error;
     res.json(results)
  });
});

// envoi des données de la table Collectionneur dans un serveur

app.get('/getCollectionneur', function (req, res) {

    connection.query('SELECT * FROM Collectionneur', function (error, results) {
      if (error) throw error;
     res.json(results)
    });
});


const port = 3004;

app.listen(process.env.PORT || port, () => console.log(`server is listening on ${port}`));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>