const App = () => {
  const sayHi = (e) => {
    e.preventDefault()
    window.alert('Hello！');
  }

  return (
    <div>
      <a href="https://israynotarray.com/" onClick={ sayHi }>點我</a>
    </div>
  )
}

const app = document.querySelector('#app');
const root = ReactDOM.createRoot(app);
root.render(<App />);