async-puzzles.js

const EventEmmitter = require('events');
 
async function test(val) { console.log('A', val) }
setImmediate(() => console.log('B'));
 
const ee = new EventEmmitter();
ee.on('foo', async (val) => {
  process.nextTick(() => test(val), val++);
  await test(val++);
  test(val);
});
 
new Promise((res) => {
  for (let i = 0; i < 1e9; i++) {}
  setImmediate(() => console.log('C'));
  process.nextTick(() => res('D'));
  console.log('E');
}).then(console.log);
 
process.nextTick(() => console.log('F'));
 
(async (res) => {
  for (let i = 0; i < 1e6; i++) {}
  process.nextTick(() => console.log('G'));
  console.log('I')
  return 'H';
})().then(console.log);
 
process.nextTick(() => console.log('I'));
 
const promises = [];
let n = 0;
for (; n < 10; n++) promises.push(test(n))
setTimeout((val) => ee.emit('foo', val), 1000,  n);
ee.emit('foo', 123)
console.log('J');
Promise.all(promises);