function delay(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

const then = Date.now();

async function task(name, input) {
  console.log(`[${Date.now() - then}] ${name}: start, input: ${input}`);
  await delay(1_000);
  console.log(`[${Date.now() - then}] ${name}: done, input: ${input}`);
  return input + name;
}

let token = 0;
async function onUpdate(input) {
  let current = ++token;
  async function* gen() {
    let result = await task('a', input);
    yield;
    result = await task('b', result);
    yield;
    result = await task('c', result);
    console.log(`[${Date.now() - then}] final result: ${result}`);
    return result;
  }
  for await (const _ of gen()) {
    if (token !== current) break;
  }
}

onUpdate('1');
await delay(500);
onUpdate('2');
await delay(2_000);
onUpdate('3');