myAsync.js

function myAsync(generatorFactory) {
  return (...args) => {
    const generator = generatorFactory(...args);
    const resolve = (result) => {
      if (result.done) {
        return Promise.resolve(result.value);
      }
      return Promise.resolve(result.value)
        .then((resolvedValue) => resolve(generator.next(resolvedValue)))
        .catch((error) => generator.throw(error));
    };
    return resolve(generator.next());
  };
}

// example
const fetchResult = myAsync(function* (param) {
  yield new Promise((resolve) => setTimeout(resolve, 1000));
  return `{ data: ${param} }`;
});

const main = myAsync(function* () {
  const result = yield fetchResult("123");
  console.log("result is: " + result);
});

main();