一、函数式组件

this指向为undefined

<!DOCTYPE html>
<html lang="zh">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>函数式组件</title>
    </head>
    <body>
        <div id="test"></div>
        <script type="text/javascript" src="js/react.development.js"></script>
        <script type="text/javascript" src="js/react-dom.development.js"></script>
        <script type="text/javascript" src="js/babel.min.js"></script>
        <script type="text/babel">
            function Demo(){
                console.log(this)
                return <h2>我是函数式组件</h2>
            }
            ReactDOM.render(<Demo />,document.getElementById('test'))
        </script>
    </body>
</html>

二、类式组件

React使用render会自动创建实例，this指向的是类式组件实例的对象

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <title>类式组件</title>
    </head>
    <body>
        <div id="test"></div>
        <script type="text/javascript" src="js/react.development.js"></script>
        <script type="text/javascript" src="js/react-dom.development.js"></script>
        <script type="text/javascript" src="js/babel.min.js"></script>
        <script type="text/babel">
            class Demo extends React.Component{
                    render(){
                        console.log(this)
                        return <h2>我是类式组件</h2>
                    }
                }
            ReactDOM.render(<Demo/>,document.getElementById('test'))
        </script>
    </body>
</html>

React-组件

一、函数式组件

二、类式组件