学习react 笔记三

Posted 2022-06-08 奥特曼　

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一、组件

定义组件的两种方式

1.函数组件

const Ren = function () 
  return (<div>奥特曼</div>)

2.类组件

class Head extends Component 
  render () 
    return (
      <div>我是封装出来的组件</div>
    )

使用的话直接当成标签来用就好了注意首字母大写哈

const root = ReactDOM.createRoot(document.getElementById('root'))

root.render(
  <React.StrictMode>
    <Ren />
    <Head></Head>
  </React.StrictMode>
)

二、父传子

定义形式 <组件名属性名=属性值></组件名>

import React,  Component  from 'react'
import ReactDOM from 'react-dom/client' //配合ceact把react 元素渲染到dom


import SonFirst from './02、子组件1'
import SonSecond from './02、子组件2'
import Third from './02、子组件3'
class Father extends Component 
  state = 
    userInfo: 
      name: '奥特曼'
    ,
    tags: <h1>奥特曼</h1>
  
  render () 
    return (
      <div>
        我是父组件 class类
        /* 定义形式 属性名=属性值 */
        <SonFirst num=1></SonFirst>
        <SonSecond userInfo=this.state.userInfo></SonSecond>
        <Third tags=this.state.tags></Third>
      </div >
    )
  


const root = ReactDOM.createRoot(document.getElementById('root'))

root.render(
  <React.StrictMode>
    <Father />
  </React.StrictMode>
)

类组件接收

/* eslint-disable react/prop-types */
import React,  Component  from 'react'

export default class Son extends Component 
  render () 
    return (
      <div>
        this.props.num
        我是子组件
      </div>
    )

通过 this.props.num 接收

函数组件接收

/* eslint-disable react/prop-types */
import React from 'react'

export default function Son (props) 
  return (
    // eslint-disable-next-line react/prop-types
    <div>
      props.num
      我是函数的子组件
    </div>
  )

事件参数第一个参数就是 props对象

props 可以传递数字、字符串、布尔类型、数组、对象、函数、jsx

不可以直接修改 props穿过来的值若想修改可以传递方法去修改父组件的值

传递jsx

父

import Son from './04、子组件'
export default class Father extends Component 
  render () 
    return (
      <div>
        <Son>
          <h1>奥特曼噢噢噢噢~~</h1>
        </Son>
      </div>
    )

子

/* eslint-disable react/prop-types */
import React,  Component  from 'react'

// props的children 类似于 slot 插槽·
export default class Son extends Component 
  render () 
    console.log(this.props)
    return (
      <div>
        this.props.children
      </div>
    )

子组件可以直接去使用哈

传递方法demo

父

import React,  Component  from 'react'
import ReactDOM from 'react-dom/client' //配合ceact把react 元素渲染到dom


import Son from './05、子组件'
class Father extends Component 
  state = 
    list: [ id: 1, name: '迪迦', num: 10, price: 9 ,  id: 2, name: '雷欧', num: 5, price: 10 ,  id: 3, name: '泰罗', num: 6, price: 7 ],
    allPrice: 0
  
  accPrice = (price) => 
    console.log(price, this.state.allPrice)
    this.setState(
      allPrice: this.state.allPrice + price
    )
  
  addNum = (idx) => 
    let arr = [...this.state.list]
    arr[idx].num++
    this.setState(
      arr
    )
  
  render () 
    const  list  = this.state
    return (
      <>
        list.map((it, idx) => 
          return <Son accPrice=this.accPrice addNum=this.addNum idx=idx info=it key=it.id></Son>
        )
        <div>总价：list.reduce((acc, it) => acc + it.num * it.price, 0)</div>
      </>
    )
  


const root = ReactDOM.createRoot(document.getElementById('root'))

root.render(
  <React.StrictMode>
    <Father />
  </React.StrictMode>
)

子

/* eslint-disable react/prop-types */
import React,  Component  from 'react'

export default class Son extends Component 
  add = () => 
    console.log(this.props)
    this.props.addNum(this.props.idx)
  
  render () 
    console.log(this.props)
    const  info, idx  = this.props
    // this.props.accPrice(info.price * info.num)

    return (
      <div>
        <div style= padding: '20px', width: '400px', border: '1px solid #000' >
          <div >
            <div> 名字: info.name</div>
            <div> 数量: info.num  <button onClick=this.add>+1</button> </div>
            <div> 价钱: info.price</div>
            <div> 总价: info.price * info.num </div>
          </div>
        </div >
      </div>
    )

props的三个特点：

1.可以传任何内容

2.只读的，不可以直接修改

3.遵守单项数据流原则（一层一层往下传）

三、兄弟传值

兄弟传值 a组件使用父组件的值 b组件通过父组件的传递过来的方法进行修改没有像vue中的vuex、eventbus

父

import React,  Component  from 'react'
import ReactDOM from 'react-dom/client' //配合ceact把react 元素渲染到dom


import Son1 from './06、兄弟1'
import Son2 from './06、兄弟2'
class Father extends Component 
  state = 
    num: 1
  

  addNum = () => 
    this.setState(
      num: this.state.num + 1
    )
  
  render () 
    const  list  = this.state
    return (
      <>
        <Son1 addNum=this.addNum ></Son1>
        <Son2 num=this.state.num></Son2>

      </>
    )
  


const root = ReactDOM.createRoot(document.getElementById('root'))

root.render(
  <React.StrictMode>
    <Father />
  </React.StrictMode>
)

子1

/* eslint-disable react/prop-types */
import React,  Component  from 'react'

export default class SON extends Component 
  add = () => 
    this.props.addNum()
  
  render () 
    return (
      <div>
        <button onClick=this.add>数量加1</button>
      </div>
    )

子2

/* eslint-disable react/prop-types */
import React,  Component  from 'react'

export default class SON extends Component 
  render () 
    return (
      <div>
        this.props.num
      </div>
    )

四、跨级传值

使用方法

1. 导入并调用createContext方法从结果中结构出 provider，consumer 组件

import React,  createContext  from 'react'
const  Provider, Consumer  = createContext()

2. 使用Provider 组件包裹根组件并通过value属性提供要共享的数据

 return (
        <Provider value= 传递的数据 >
          <根组件的内容 />
        </Provider>
    )

记得导出 export Consumer

3.在任意后代组件中使用第1步导出Consummer组件在包裹住整个组件

import  Consumer  from './07、跨级传值'

export default class Parent extends React.Component 

  render () 
    return (
      <Consumer>
        
          (data) => 
            console.log(data)
            return (
              <>
                  内容
              </>
            )
          
        
      </Consumer>)

demo

顶层组件

import React,  Component, createContext  from 'react'
import ReactDOM from 'react-dom/client' //配合ceact把react 元素渲染到dom
const  Provider, Consumer  = createContext()

import Fathers from './07、子组件'

class Grandpa extends Component 
  state = 
    num: 1
  

  addNum = (number) => 
    this.setState(
      num: this.state.num + number
    )
  
  render () 
    return (
      <>
        <Provider value= num: this.state.num, add: this.addNum >
          <Fathers></Fathers>
        </Provider>
      </>
    )
  

export  Consumer 
const root = ReactDOM.createRoot(document.getElementById('root'))

root.render(
  <React.StrictMode>
    <Grandpa />
  </React.StrictMode>
)

父组件

import React from 'react'
import ReactDOM from 'react-dom'
import Son from './07、孙组件'
import  Consumer  from './07、跨级传值'
export default class Parent extends React.Component 
  state = 
    num: 1
  

  addNum = () => 
    this.setState(
      num: this.state.num + 1
    )
  
  render () 
    return (
      <Consumer>
        
          (data) => 
            console.log(data)
            return (
              <>
                <div onClick=() => data.add(100)>我是Father组件-data.num</div>
                <Son></Son>
              </>
            )
          
        
      </Consumer>)

子组件

import React,  Component, createContext  from 'react'
import ReactDOM from 'react-dom/client' //配合ceact把react 元素渲染到dom
import  Consumer  from './07、跨级传值'


export default class Son extends Component 
  state = 
    num: 1
  

  addNum = () => 
    this.setState(
      num: this.state.num + 1
    )
  
  render () 
    return (
      <Consumer>
        
          (data) => 
            console.log(data)
            return (
              <div onClick=() => data.add(100)>我是son组件-data.num</div>
            )
          
        
      </Consumer>)

抽离跨级组件

import React from 'react'
const  Provider, Consumer  = React.createContext()
export  Provider, Consumer

父组件

import React,  Component, createContext  from 'react'
import ReactDOM from 'react-dom/client' //配合ceact把react 元素渲染到dom
import  Provider  from './08、context'
import Son from './08、子组件'
class Father extends Component 
  state = 
    num: 1
  

  addNum = () => 
    this.setState(
      num: this.state.num + 1
    )
  
  render () 
    return (
      <>
        <Provider value=this.state.num>
          <Son></Son>
        </Provider>
      </>
    )
  


const root = ReactDOM.createRoot(document.getElementById('root'))

root.render(
  <React.StrictMode>
    <Father />
  </React.StrictMode>
)

子组件


import  Consumer  from './08、context'
import React,  Component  from 'react'
export default class Son extends Component 
  render () 
    return (
      <Consumer>
        
          (data) => 
            return (
              <>
                <div onClick=() => data.add(100)>我是Son组件-data</div>
              </>
            )
          
        
      </Consumer>)

推荐插件

在项目中打出rcc rfc 就可以快捷创建代码啦

rcc： create class Componet

rfc： create function Componet

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