VYV7

// making an HTTP request using Fetch API

const aThing = fetch('http://restcountries.eu/rest/v2/all', {})
.then( (response) => {                              // THEN 1
    // fetch returns fulfilled Promise even if 
    // the server responds with an error - check the status
    if (response.status === 200) {
        return response.json()
    } else {
        throw Error('Something went wrong ;(')

VYV7

// This corresponds to promiseExecutor
promExec = function ( successCb, failureCb ) {
    setTimeout( () => {                                         // run when stack is clear
        if (1)  successCb('Promise resolved', then2successCb)   // called if things went well
        else    failureCb('Promise rejected')                   // called if things went bad
    }, 0)
}

// THEN 1
const then1successCb = function ( resolveMessage, successCb ) {  // SUCCESS Handler

VYV7

//=============================================================================
// Executor function is called right away when a promise is created
// Start async process here
// (HTTP requests, storing data to a database etc.)
// EXECUTOR 1------------------------------------------------------------------
const promiseExecutor1 = (resolve, reject) => {
    console.log('Strating 1st async operation (promiseExecutor1)')
    setTimeout( () => {                             // start 1st async task
        console.log('\n1st async operation DONE')
        if (1)  resolve('Promise 1 resolved')       // called if things went well

VYV7

// making an HTTP request


// create instance of the request and initialise it
const myRequest = new XMLHttpRequest()
console.log('New request object:')                          // DEBUG
console.log(myRequest)                            // DEBUG (comment out sent())

// onload event (handles the response if readyState is DONE)
myRequest.onload = () => {

VYV7

// making an HTTP request


// create instance of the request
const myRequest = new XMLHttpRequest()
console.log('New XMLHttpRequest object:')                   // DEBUG
console.log(myRequest)                            // DEBUG (comment out sent())

// onload event (handles the response if readyState is DONE)
myRequest.onload = () => {

VYV7

//---------------------------------------------------------
// define what to do when the promise is resolved/rejected
// Promise.then( onFulfilled(), onRejected() ).catch()
let message

myPromise
.then( (resolveMessage) => { 
    message = `Then1: ${resolveMessage}`
    console.log('\n' + message)
    console.log(myPromise)

VYV7

//---------------------------------------------------------
// Executor function is called right away when a promise is created
// Start a long running process here
// (HTTP requests, storing data to a database etc.)
const promiseExecutor = (resolve, reject) => {
    setTimeout( () => {
        if (1) {
            resolve('Promise resolved') // called if things went well
        } else {
            reject('Promise rejected')  // called if things went bad