<div id="app"></div>
class App extends React.Component {
constructor(props) {
const [count, setCount] = React.useState(0);
super(props);
this.state = {
count: 0,
};
}
sayHi() {
window.alert('Hello Ray.');
}
render() {
return (
<div>
<button type="button" onClick={ this.sayHi }>打招呼</button>
</div>
);
}
}
const app = document.querySelector('#app');
const root = ReactDOM.createRoot(app);
root.render(<App />);
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