Async Without Promise

function doAsyncTask(callback: () => void): void {
  setTimeout(() => {
    console.log('Async task done');
    callback();
  }, 1000);
}

function onComplete(): void {
  console.log('Callback executed');
}

doAsyncTask(onComplete);

Version WITH promise:

function doAsyncTask(): Promise<void> {
  return new Promise((resolve) => {
    setTimeout(() => {
      console.log('Async task done');
      resolve();
    }, 1000);
  });
}

function onComplete(): void {
  console.log('Promise resolved');
}

doAsyncTask().then(onComplete);