react 学习：react 生命周期

import React from 'react'

/**
 *
 */
class DigitalClock extends React.Component{


    constructor(props){
        super(props)
        this.state={
            date:new Date()
        }
    }

    componentDidMount(){
        this.timer=setInterval(()=>{
            this.setState({
                date:new Date()
            })
        },3000)
    }
    componentDidUpdate(currentState){
        console.log(currentState)
    }
    componentWithUnmount(){
        clearInterval(this.timer)
    }

    render(){
        return (
            <div className="digital-clock-component jumbotron">
                <h1>{this.state.date.toLocaleString()}</h1>
            </div>
        )
    }



}

export default DigitalClock

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';
import NameCard from './components/NameCard';
import LikesButton from './components/LikeButton';
import DigitalClock from './components/DigitalClock';
const tags=['男神']
class App extends Component {

  render() {
    return (
      <div className="App">
         <div className={"App-header"}>
             <img src={logo} className={"App-logo"} alt={"logo"}/>
             <h2>欢迎来到矿洞程序员</h2>
             {/*<NameCard name="chenxiaoyang" number={123456} isHuman tags={tags} />*/}
             {/*<LikesButton/>*/}
             <DigitalClock/>
         </div>
         </div>
    );
  }
  }

export default App;