JS AwaitAll is all what we want.

awaitall.js

const timeout = ms =>
  new Promise((resolve, reject) => setTimeout(() => resolve(), ms));

async function f() {
  await timeout(500);
  return 'f';
}

async function g() {
  await timeout(1000);
  return 'g';
}

async function main() {
  const [x, y] = await Promise.all([f(), g()]);
  // Actually, I wanted to write this:
  //const [x, y] = awaitall f(), g();
  console.log(x);
  console.log(y);
}

main();