javascript async script

1(async () => {
2  let response = await fetch('/article/promise-chaining/user.json');
3  let user = await response.json();
4  ...
5})();

1<script async src="script.js"></script>

1function hello() {
2  return new Promise((resolve,reject) => {
3    setTimeout(() => {
4      resolve('I am adam.');
5    }, 2000);
6  });
7}
8async function async_msg() {
9  try {
10    let msg = await hello();
11    console.log(msg);
12  }
13  catch(e) {
14    console.log('Error!', e);
15  }
16}
17async_msg(); //output - I am adam.

1<script src="demo_async.js" async></script>

1<script src="demo_defer.js" defer></script>