JS Promises

let myPromise = new Promise(function(myResolve, myReject) {
/* "Producing Code" (May take some time) */

  myResolve(); /* when successful */
  myReject();  /* when error */
});

/* "Consuming Code" (Must wait for a fulfilled Promise) */
myPromise.then(
  function(value) { /* code if successful */ },
  function(error) { /* code if some error */ }
);

myPromise.then(
  function(value) { /* code if successful */ },
  function(error) { /* code if some error */ }
);

setTimeout(function() { myFunction("I love You !!!"); }, 3000);

function myFunction(value) {
  document.getElementById("demo").innerHTML = value;
}

let myPromise = new Promise(function(myResolve, myReject) {
  setTimeout(function() { myResolve("I love You !!"); }, 3000);
});

myPromise.then(function(value) {
  document.getElementById("demo").innerHTML = value;
});

function getFile(myCallback) {
  let req = new XMLHttpRequest();
  req.open('GET', "mycar.html");
  req.onload = function() {
    if (req.status == 200) {
      myCallback(req.responseText);
    } else {
      myCallback("Error: " + req.status);
    }
  }
  req.send();
}

getFile(myDisplayer);

let myPromise = new Promise(function(myResolve, myReject) {
  let req = new XMLHttpRequest();
  req.open('GET', "mycar.htm");
  req.onload = function() {
    if (req.status == 200) {
      myResolve(req.response);
    } else {
      myReject("File not Found");
    }
  };
  req.send();
});

myPromise.then(
  function(value) {myDisplayer(value);},
  function(error) {myDisplayer(error);}
);