See scheduling of callbacks/microtasks/tasks

tasks-and-queues.js

(() => {
  console.log('script start');

  setTimeout(function() {
    console.log('setTimeout');
  }, 0);

  // Edge/IE only
  // setImmediate(function() {
  //   console.log('setImmediate');
  // });

  Promise.resolve().then(function() {
    console.log('promise1');
  }).then(function() {
    console.log('promise2');
  });

  console.log('script end');

  const evt = new Event('test')
  const evtListener = () => console.log('click handler')
  document.addEventListener('test', evtListener)
  document.dispatchEvent(evt)
  document.removeEventListener('test', evtListener)
})()