React JSX简单案例演示

由于 JSX 就是 JavaScript，一些标识符像 class 和 for 不建议作为 XML 属性名。
作为替代，React DOM 使用 className 和 htmlFor 来做对应的属性。

要将 React 元素渲染到根 DOM 节点中，我们通过把它们都传递给 ReactDOM.render() 的方法来将其渲染到页面上
如果需要嵌套多个 HTML 标签，需要使用一个 div 元素包裹它
元素可以添加自定义属性，需要使用 data- 前缀

import React, { Component } from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';


  ReactDOM.render(
    <div>
      <h1>cyy</h1>
      <p data-level="很菜">learn react</p>
    </div>,
    document.getElementById('example')
  );


// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();

可以在 JSX 中使用 JavaScript 表达式
表达式写在花括号 {} 中

import React, { Component } from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';


  ReactDOM.render(
    <div>
      <p>{1+1}</p>
    </div>,
    document.getElementById('example')
  );


// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();

在 JSX 中不能使用 if else 语句，但可以使用 conditional (三元运算) 表达式来替代。

import React, { Component } from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';

  const i=1;
  ReactDOM.render(
    <div>
      <p>{i===1?'true':'false'}</p>
    </div>,
    document.getElementById('example')
  );


// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();

React 推荐使用内联样式
可以使用 camelCase 语法来设置内联样式
React 会在指定元素数字后自动添加 px

import React, { Component } from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';

  var style={
    color:'#fff',
    backgroundColor:"lightblue",
    fontSize:14
  };

  ReactDOM.render(
    <div>
      <p style={style}>this is a test</p>
    </div>,
    document.getElementById('example')
  );


// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();

通过 style 添加内联样式的时候，容易犯的错误

这样直接写在里面，注意是有两个花括号

注释需要写在花括号中，话说回来添加注释我一般都使用快捷键ctrl+问号

貌似一般正经的编辑器都是支持的

哈哈

JSX 允许在模板中插入数组，数组会自动展开所有成员

import React, { Component } from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';

  var arr=[
    <h1>this is h1</h1>,
    <p>this is p</p>
  ];

  ReactDOM.render(
    <div>
      {arr}
    </div>,
    document.getElementById('example')
  );

serviceWorker.unregister();