How to “await” for a callback to return?

async/await is not magic. An async function is a function that can unwrap Promises for you, so you’ll need api.on() to return a Promise for that to work. Something like this:

function apiOn(event) {
  return new Promise(resolve => {
    api.on(event, response => resolve(response));
  });
}

Then

async function test() {
  return await apiOn( 'someEvent' ); // await is actually optional here
                                      // you'd return a Promise either way.
}

But that’s a lie too, because async functions also return Promises themselves, so you aren’t going to actually get the value out of test(), but rather, a Promise for a value, which you can use like so:

async function whatever() {
  // snip
  const response = await test();
  // use response here
  // snip
}