express js with mysql code example

Example 1: how to manage a db connection in javascript

//put these lines in a seperate file
const mysql = require('mysql2');

const connection = mysql.createPool({
    host: "localhost",
    user: "",
    password: "",
    database: ""
    // here you can set connection limits and so on
});

module.exports = connection;

//put these on destination page
const connection = require('../util/connection');

async function getAll() {
    const sql = "SELECT * FROM tableName";
    const [rows] = await connection.promise().query(sql);
    return rows;
} 
exports.getAll = getAll;

Example 2: how to access a database in express

var MongoClient = require('mongodb').MongoClient

MongoClient.connect('mongodb://localhost:27017/animals', function (err, client) {
  if (err) throw err

  var db = client.db('animals')

  db.collection('mammals').find().toArray(function (err, result) {
    if (err) throw err

    console.log(result)
  })
})

Example 3: how to access a database in express

var mysql = require('mysql')
var connection = mysql.createConnection({
  host: 'localhost',
  user: 'dbuser',
  password: 's3kreee7',
  database: 'my_db'
})

connection.connect()

connection.query('SELECT 1 + 1 AS solution', function (err, rows, fields) {
  if (err) throw err

  console.log('The solution is: ', rows[0].solution)
})

connection.end()