react项目实战学习笔记-学习3-知识点回顾3

类组件

import React,{Component, Fragment, useState} from "react"
 
 
class App extends Component{
    state={
        num:1
    }
    onClick=()=>{
        this.setState({
            num:this.state.number+1
        })
    }
    render(){
        return (
            <>
            <h1>{this.state.number}</h1>
            <button onClick={this.onClick.bind(this)}></button>
            </>
        )
    }
}
 
export default App

函数组件

import React,{Component, Fragment, useState} from "react"
 
 
function App(){
  const [num,setNum]=useState(1)
  const addNum=()=>{
    setNum((num)=>num+1)
  }
  return(
    <>
    <h1>数字为:{this.state.num}</h1>
    <button onClick={{addNum}}>累加</button>
    </>
    
  )
}
export default App

useRef获取到子组件