前端学习（2217）：react元素渲染之时钟

index.js

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';

//<app/>js的普通对象
/*let app = < App / >
    let root = document.getElementById('root')

    let h1=<h1>helloworld<span>我是</span></h1>
{ ReactDOM.render(
    h1, root
); }*/
//实现时刻的变化
function clock() {
    let time = new Date().toLocaleTimeString()
    let element = ( < div > < h1 > 现在的时间 { time } < /h1></div > )
    let root = document.querySelector('#root')
    ReactDOM.render(
        element, root
    )
}
clock()

setInterval(clock, 1000)

运行结果