lovecoding
/
w1020


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./babel.min.js"></script>
    <script src="./react.development.js"></script>
    <script src="./react-dom.development.js"></script>
</head>

<body>
    <div id="root"></div>
    <script type="text/babel">
        const root = ReactDOM.createRoot(document.getElementById("root"));
        function App() {
            return (
                <div>
                    <Count num={5} />
                </div>
            )
        }
        class Count extends React.Component {
            constructor(props) {
                super(props);
                this.state = {
                    count: 0
                }
            }
            handleAdd() {
                // this.setState({
                //     count: this.state.count + 1
                // })
                this.setState((prevState, props) => {
                    console.log(prevState, props, '打印1')
                    return {
                        count: prevState.count + props.num
                    }
                })
            }
            render() {
                return (
                    <div>
                        <p>
                            <button onClick={this.handleAdd.bind(this)}>+</button>
                            {this.state.count}
                            <button>-</button>
                        </p>
                    </div>
                )
            }
        }
        root.render(<App />);
    </script>
</body>

</html>