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+<!DOCTYPE html>
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+<html lang="en">
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+
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+<head>
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+ <meta charset="UTF-8">
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+ <meta name="viewport" content="width=device-width, initial-scale=1.0">
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+ <title>Document</title>
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+ <script src="./babel.min.js"></script>
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+ <script src="./react.development.js"></script>
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+ <script src="./react-dom.development.js"></script>
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+</head>
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+
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+<body>
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+ <div id="root"></div>
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+ <script type="text/babel">
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+ let root = ReactDOM.createRoot(document.getElementById("root"));
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+ class Count extends React.Component {
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+ // 给类组件添加状态 构造器函数 用于初始化实例的
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+ constructor(props) {
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+ // 通过this访问当前创建的实例 但是 一定要 在调用super函数后才可以使用this
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+ super(props);
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+ // 组件自身的状态
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+ this.state = {
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+ a: 'hi'
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+ }
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+ }
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+ render() {
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+ console.log(this)
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+ // 获取 状态 this组件实例的state属性
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+ let {a} = this.state;
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+ return (
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+ <div>
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+ <p>展示:{a}</p>
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+ {/**<p>展示:{this.state.a}</p>*/}
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+ </div>
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+ )
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+ }
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+ }
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+ root.render(<Count/>);
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+ </script>
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+</body>
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+
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+</html>
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zheng