console 命令行工具 X clear

console

const {useState} = React;


const MyComponent  = () => {
    const [flag, setFlag] = useState(false);

    function dealClick() {
        setFlag(!flag);
    }

    return (
        <button onClick={dealClick}>{flag ? "true" : "false"}</button>
    );
}



class App extends React.Component {
  
  render() {
    return (
    	<div>
      	<h3>{flag}</h3>
          <MyComponent/>
      </div>
    );
  }
}


ReactDOM.render(
	<App/> ,
	document.getElementById('example')
);

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello React!</title>
<script crossorigin src="https://unpkg.com/react@17/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@17/umd/react-dom.development.js"></script></head>
<body>

<div id="example"></div>
</body>
</html>