前端学习（2227）：react之状态二

import React from 'react';
import ReactDOM from 'react-dom';


class Clock extends React.Component {
    constructor(props) {
        super(props)
            //状态 时间

        this.state = {
            time: new Date().toLocaleTimeString()
        }
        console.log(this.state.time)
    }
    render() {
            return ( <
                div >
                <
                h1 > 当前时间 { this.state.time } < /h1> < /
                div >

            )

        }
        /* 生命周期函数 */
    componentDidMount() {
        setInterval(() => {
            console.log(this.state.time)
                // this.state.time = new Date().toLocaleTimeString() <
            this.setState({
                    time: new Date().toLocaleTimeString()
                })
                // console.log(this.state.time)
        }, 1000)
    }
}




//console.log("这是渲染函数")
ReactDOM.render( < Clock / > , document.querySelector("#root"))

运行结果