Promises in JavaScript and NodeJS

I am retriving data from a DB. I am using promise to return the data back to the client when the data is ready:

var http = require('http');
var mysql = require('mysql');


var con = mysql.createConnection({
  host: "localhost",
  user: "root",
  password: "******",
  database: "heroes"
});



let myPromise = new Promise(function(myResolve, myReject) {
    con.connect(function(err) {
      if (err) throw err;
      con.query("SELECT id, name FROM heroes", function (err, result, fields) {
        if (err) throw err;
        console.log(result);
        myResolve(JSON.stringify(result));
      });
    });
});




http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/html'});

  myPromise.then(result => res.end(result))
   
    
  
}).listen(8080);

I have learned that you are supposed to supply two call-back functions to the Promise and that these are optional arguments in case of success or failure.

When I am calling myResolve() (which doesn't exist in this case), the data is being sent back to the client fine using .then(). Nonetheless, when I am not calling myResolve() something doesn't work and the page is being refreshed forever.

A. If these are indeed callbacks, how can I call a non exsiting function such as myResolve() ? Why I can't extract result without calling this function ?

B. How can I execute the database query only after there is a request on the 8080 port ? When I am trying to insert the promise into a function, I can't use .then (I am assuming the function by itself doesn't have any promise to give obiously).

Code Edit for the second question:

function connectToDB()
{
    let myResult;
    
    let myPromise = new Promise(function(myResolve, myReject) {
        con.connect(function(err) {
          if (err) throw err;
          con.query("SELECT id, name FROM heroes", function (err, result, fields) {
            if (err) throw err;
            console.log(result);
            myResolve(JSON.stringify(result));
            myResult = result;
          });
        });
    });
    
    return myResult;
}

Final code edit after wraping the promise with a function:

function connectToDB()
{

    
    let myPromise = new Promise(function(myResolve, myReject) {
        con.connect(function(err) {
          if (err) throw err;
          con.query("SELECT id, name FROM heroes", function (err, result, fields) {
            if (err) throw err;
            console.log(result);
            myResolve(JSON.stringify(result));

          });
        });
    });
    
    return myPromise;
}

Edit:

The questions are still valid, regardless of the use of res.send or res.end, as far as I understand it has got nothing to do with what I am asking about.