JS async/await inquiry

Question

I'm working with an api to do an async upload, but the api does not use promises so I can't easily do an await on it. The api calls an onComplete callback instead.

My functions look something like this:

let barStatus = "not started";

fun doAsyncBar() {
  barStatus = "loading";
  // do something async 
}

fun onBarFinished() {
  barStatus = "finished";
}

async isBarFinished() {
  while(barStatus != "finished") {
    await sleep(10)
  }
  return true;
}

async foo() {
  const bar = doAsyncBar();

  const barFinished = await isBarFinished();

  // do something else 
}

My current code works, but I'm curious what would be the best practice for this scenario. Thank you!