node.js is a server that runs javascript on the server

1. bun is a replacement for node.js
   https://bun.sh

2. generally nodejs is installed via yum, dnf, or whatever package
   manager you have

3. node.js is javascript engine that runs javascript on the server side

4. To setup a project
   npm init

5. install express server
   npm install express --save
   see https://expressjs.com

6. Here is "Hello World!" using an express server
  See https://expressjs.com
 
const express = require('express')
const app = express()
const port = 3000

##
## App get sets a route for /
app.get('/', (req, res) => {
  res.send('Hello World!')
})

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`)
})

7. BUT - really nobody uses the simple version...
   we use express-generator
   # install express-generator
   >npm install -g express-generator
   # run install
   >express

   This generates a structure in the current directory including:
   routes
   views
   bin
   public
   node_modules

   a) public is for static html files

   b) routes defines how to route urls

   c) bin
      bin/www is what starts the server
      
8. nodemon - sets up node so that it will reread files
   upon change.
   > npm install --save-dev nodemon
   
9. Fetching data from the database.
   a) create an object that fetches data ( file con.js)
   
   var mysql = require('mysql2');
   var con = mysql.createConnection({
           host:'localhost',
           user: 'xxxxxuser',
       password:'yyyypass',
       database:'foodb'
   });


   con.connect(function(err) {
      if (err) throw err;
   });

   async function sqlquery(sql)
   {
      const results = await con.promise().query(sql);
     // returns a list of [data,meta]
      return results[0];
   }

   module.exports = {
       sqlquery
   }

   b) from routes/index.js
     var con = require("../services/con");
     router.get('/fubar', async function(req,res,next) {
        let sql = 'show tables';                   
        res.json(await con.sqlquery(sql));                   
     });

  c) await can only be used from an aync function
     the function being called needs to be async
     and we do an await on a promise from con.query...
     the results returned are a list of elements, data, and meta data
     This appears complex.
     basically the mysql query is run in the background unless
     we force nodejs to wait for the results