const main = (fn) => {
  return fn();
};

const result = main(() => {
  return 42;
});
console.log(result); // 42

const resutl2 = main(async () => {
  return 'hello';
});
console.log(resutl2); // Promise { 'hello' }

const fn = async () => {
  const result3 = await main(async () => {
    // return Promise.resolve('world');
    return new Promise((resolve) => {
      setTimeout(() => {
        resolve('world');
      }, 1000);
    });
  });
  console.log(result3); // world
};
fn();

const fn2 = (t) => {
  if (t === 1) return 'hello';
  if (t === 2) return Promise.resolve('world');
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve('world');
    }, 1000);
  });
};

const rfn2 = async () => {
  console.log('\\\\\\\\'); // hello
  console.log('1', fn2(1)); // hello
  console.log('2', await fn2(2)); // hello
  console.log('3', await fn2(3)); // Promise { <pending> }
  console.log('-----------'); // world
};
rfn2();