This gist simulates the execution of two async methods using promises. It returns a message of success when both complete. A random timeout between 1 and 3000ms is being used.

promiseTest.js

function randomTimeout() {
  const t = Math.floor(Math.random() * 3000 + 1);
  return t;
}

const method1 = new Promise(resolve => {
  timeout = randomTimeout();
  setTimeout(() => resolve("method1"), timeout);
});

const method2 = new Promise(resolve => {
  timeout = randomTimeout();
  setTimeout(() => resolve("method2"), timeout);
});

Promise.all([
  method1.then(result => console.log(result)),
  method2.then(result => console.log(result))
]).then(() => console.log("Success"));