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要使用React需要引入React所对应的文件
这两个标签就是加载react
<script src="https://unpkg.com/react@17/umd/react.development.js" crossorigin></script>
<script src="https://unpkg.com/react-dom@17/umd/react-dom.development.js" crossorigin></script>
基本使用
reactDOM提供了与浏览器交互的DOM功能,渲染DOM,虚拟DOM
ReactDOM.render() 中有三个参数
第一:要渲染的内容
第二:要渲染的内容存放的容器
第三:渲染后的回调函数,可选参数
<!DOCTYPE html>
<html lang="en">
<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>Document</title>
<script src="https://unpkg.com/react@17/umd/react.development.js" crossorigin></script>
<script src="https://unpkg.com/react-dom@17/umd/react-dom.development.js" crossorigin></script>
<script src="like_button.js"></script>
</head>
<body>
<!-- react.js 提供核心代码 -->
<div id="root"></div>
<script>
ReactDOM.render(
"今天是阴天",
document.querySelector('#root'),
()=>{
console.log('ok')
}
)
</script>
</body>
</html>
动态创建视图标签
React.createElement 三个参数{传入HTML标签名,表示属性类型,要显示的内容}
<body>
<div id="root"></div>
<script>**加粗样式**
let h1 = React.createElement('h1',null,'React')
let q = React.createElement('h2',null,'React')
let el = React.createElement(
'header',
{id:"className"},
h1,
q)
ReactDOM.render(
el,
document.querySelector('#root'),
()=>{
console.log('ok')
}
)
</script>
</body>
JSX
引入
<script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
使用
<!DOCTYPE html>
<html lang="en">
<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>Document</title>
<script src="https://unpkg.com/react@17/umd/react.development.js" crossorigin></script>
<script src="https://unpkg.com/react-dom@17/umd/react-dom.development.js" crossorigin></script>
<!-- <script src="like_button.js"></script> -->
<script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
let str = "蛇精"
ReactDOM.render(
<h1>
<p>葫芦小金刚</p>
<p>{str}</p>
</h1>,
document.querySelector('#root'),
()=>{
console.log('ok')
}
)
</script>
</body>
</html>
JSX注意点
<div id="root"></div>
<script type="text/babel">
ReactDOM.render(
<div>
<div className="box" style={{width:'300px'}}></div>
</div>,
document.querySelector('#root')
)
React组件使用下载安装
npx create-react-app my-app
cd my-app
npm start
组件的创建方式
类组件:
1.组件类必须继承 React.Component
2.组件类必须有render方法
3.render 方法的return 后定义组件的内容
最后记得导出
import React from "react";
class Family extends React.Component{
render(){
return (<div>
<ul>
<li>one</li>
<li>two</li>
<li>three</li>
</ul>
</div>)
}
};
export default Family
显示直接引入,单标签使用双标签也ok
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';
ReactDOM.render(
<App/>,
document.getElementById('root')
);
reportWebVitals();
React事件处理
state
改变state必须通过setState
import React,{Component} from "react";
import Family from "./family";
class App extends Component{
state = {
hEight:174
}
tianjia(){
this.setState({
hEight:this.state.hEight+1
})
}
render(){
return (<div>hellow,REACT
<Family/>
<p>{this.state.hEight}</p>
<button onClick={
()=>{
this.tianjia()
}
}>点我变高</button>
</div>)
}
};
export default App;
防止this指向问题
解决
第一:
tianjia()=>(){
this.setState({
hEight:this.state.hEight+1
})
}
第二:箭头函数调用
()=>{
this.tianjia()
}
建议直接使用第一种
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