Node MySQL connection

app.js

var mysql = require('mysql');
var express = require('express');
var app = express();

var connection = mysql.createConnection({
    host : "localhost",
    user : "username",
    password: "yourpassword",
    database: "Example"
});
connection.connect(function(err) {
    if (err) throw err;
    console.log("Connected!");
});
var queryString = 'SELECT * FROM test';

// Fetching data from database
app.get('/', function(req, res) {
    connection.query(queryString, function (err, rows, fields) {
        if (err) {
            throw err;
        }
        return res.json(rows);
    });
    // connection.end();
});

//enable cross-domain request.
var allowCrossDomain = function(req, res, next) {
    res.header('Access-Control-Allow-Origin', '*');
    res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
    res.header('Access-Control-Allow-Headers', 'Content-Type');
    next();
};
app.use(allowCrossDomain);

app.listen(3000, function() {
    console.log("Server listening on port 3000");
});