Promises example

p.js

const { createHook } = require('async_hooks');
const { promisify } = require('util');
const sleep = promisify(setTimeout);

let count = 0;

const hook = createHook({
  init(id, type) {
    if (type === 'PROMISE')
      count++;
  }
});

hook.enable();

async function foo() {
  await sleep(10);
//  return Promise.resolve(5);
  return 5;
}

foo().then(console.log);

process.on('exit', () => console.log(count));

p2.js

const { createHook } = require('async_hooks');
const { promisify } = require('util');

let count = 0;
let resolves = 0;
let callbacks = 0;

const set = new Set();

const hook = createHook({
  init(id, type) {
    if (type === 'PROMISE') {
      set.add(id);
      count++;
    }
  },
  after(id) {
    if (set.has(id))
      callbacks++;
  },
  promiseResolve() {
    resolves++;
  }
});

hook.enable();

function foo() {
//async function foo() {
  return new Promise((res, rej) => {
    setTimeout(() => res(5), 10);
  });
}

foo().then(console.log);

process.on('exit', () => console.log(count, resolves, callbacks));

p3.js

const { createServer } = require('http');
const { createHook } = require('async_hooks');
const { promisify } = require('util');

let count = 0;

const set = new Set();

const hook = createHook({
  init(id, type) {
    if (type === 'PROMISE') {
      set.add(id);
      count++;
    }
  }
});

hook.enable();

createServer((req, res) => {
  foo()
    .then((d) => res.end(`${d}`))
    .catch(console.log);
}).listen(8000);

//async function foo() {
function foo() {
  return new Promise((res, rej) => {
    setTimeout(() => {
      res(count);
    }, 10);
  });
}

// function foo() == 6k requests = 18897 Promises
// async function foo() == 6k requests = 31535 Promises