Async Generator usecase: https://vercel.com/blog/ai-sdk-3-generative-ui

streaming-by-async-generator.js

const draw = (output) => console.log(output);
const getWeather = async (city) => {
  await new Promise((resolve) => setTimeout(resolve, 1000));
  return "sunny";
};

const render = async function* ({ city }) {
  yield `<Spinner />`;
  const weather = await getWeather(city);
  return `<Weather info=${weather} />`;
};

// Please draw the weather after using this `render`.
async function main() {
  const gen = render({ city: "New York" });
  while (true) {
    const { value, done } = await gen.next();
    draw(value);
    if (done) {
      break;
    }
  }
}

await main();