JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/bluebird/3.5.1/bluebird.min.js"></script>

JavaScript

const test1 = async () => {
	const time1 = new Date().getTime();
	await Promise.delay(900);
  await Promise.delay(1200);
  await Promise.delay(1600);
  const time2 = new Date().getTime();
  console.log('result 1: ', time2 - time1);
};

const test2 = async () => {
	const time1 = new Date().getTime();
  await Promise.all([Promise.delay(900), Promise.delay(1200), Promise.delay(1600)]);
  const time2 = new Date().getTime();
  console.log('result 2: ', time2 - time1);
};

test1();
test2();