React入门之React_使用es5和es6语法渲染和添加class

React入门

//react的核心库
<script src="https://cdn.jsdelivr.net/npm/react@17/umd/react.development.js"></script>
//react操作dom的核心库，类似于jquery
<script src="https://cdn.jsdelivr.net/npm/react-dom@17/umd/react-dom.development.js"></script>
//用来解析es6语法
<script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>

es5 写法

基础语法

必须要有根元素进行包裹

//创建元素

var element = React.createElement('li',{},'hello') //节点，节点属性，标签内容

//var element = React.createElement('li',null,'hello')

//渲染元素

ReactDOM.render(element,document.getElementById('root1'))

//床架年组建，使用extends继承

React.component

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 
        react渲染三步走
        1.定义一个容器用于存放虚拟dom
        2.创建虚拟dom元素
        3.把虚拟dom元素渲染到页面上
     -->
     <div id="root1"></div>
</body>
<script src="https://cdn.jsdelivr.net/npm/react@17/umd/react.development.js"></script>
<script src="https://cdn.jsdelivr.net/npm/react-dom@17/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
<script>
    //es5方法创建
    //创建元素
    var element = React.createElement('li',{},'hello')
    //渲染元素
    ReactDOM.render(element,document.getElementById('root1'))
//
</script>
</html>

多层嵌套的关系

注意如果在react中添加类名不能写class要写className，同时不能再同一个容器里渲染多个虚拟dom，必须要有根元素进行包裹

//如果有多层嵌套的关系

var li1 = React.createElement('li',null,'11111')

var li2 = React.createElement('li',{class:'list-li'},'22222')

var _ul = React.createElement('ul',{id:'list'},li1,li2)

ReactDOM.render(_ul,document.getElementById('root2'))

es6写法

注意在使用es6语法时候script必须表明type为text/balel

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
     <div id="root1"></div>
     <script type="text/babel">
         //es6方法创建,
         ReactDOM.render(
             <ul>
                 <li className='lili'>111</li>
                 <li>222</li>
             </ul> ,
             document.getElementById('root1')
         )
     </script>
     <div id="root2"></div>
     <script type="text/babel">
        //es6方法创建,jsx简单写法
        let root2=document.getElementById('root2')
       let div= <div className='hello'>
                <h1>hello react</h1>
            </div>
        ReactDOM.render(div,root2)
    </script>
</body>
<script src="https://cdn.jsdelivr.net/npm/react@17/umd/react.development.js"></script>
<script src="https://cdn.jsdelivr.net/npm/react-dom@17/umd/react-dom.development.js"></script>
<!-- 用于解析babel -->
<script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
</html>