async/await with Promise.all

async-await-promise-all.js

// In response to https://twitter.com/housecor/status/930108010558640128
function doubleAfter2Seconds(x) {
  return new Promise(resolve => {
    resolve(x * 2);
  }, 2000);
}

async function addAsync(x) {
  const { a, b, c } = await Promise.all([
    doubleAfter2Seconds(10),
    doubleAfter2Seconds(20),
    doubleAfter2Seconds(30),
  ]);
  
  return x + a + b + c;
}