react-笔记

Fragment 占位符标签 使用方法

class => className
className="input"

{/* 注释内容 */}
// 注释内容

dangerouslySetInnerHTML={{__html:item}} 可以解析 html 标签

onClick={()=>this.handleItemDelete(index)}
dangerouslySetInnerHTML={{__html:item}}>

htmlFor 点击扩大区域
输入内容

代码优化 性能优化
this.handleInputChange = this.handleInputChange.bind(this)
onClick={this.handleButtonClick}

旧代码
handleInputChange(e){
// console.log(e.target.value);
this.setState({
inputValue: e.target.value
})
}

handleButtonClick(){
this.setState({
list: [...this.state.list,this.state.inputValue],
inputValue:''
})
}

handleItemDelete(index){
let newList = [...this.state.list]
newList.splice(index,1)
this.setState({
list: newList
})
}

优化后的新代码 this.setState(()=> ({})) 使用这个优化性能

handleInputChange(e){
const inputValue = e.target.value
this.setState(()=> ({
inputValue
}))
}

handleButtonClick(){
this.setState((prevState)=>{
return {
list: [...prevState.list,prevState.inputValue],
inputValue:''
}
})
}

handleItemDelete(index){
this.setState((prevState)=>{
let list = [...prevState.list]
list.splice(index,1)
return {
list
}
})
}

--------------------

传递参数给子组件
return index={index}
key={index}
content={item}
deleteItem= {this.handleItemDelete} />

接收父组件传递的参数和方法
import React, { Component } from 'react'
export default class TodoItem extends Component {

constructor(props){
super(props)
this.handleClick = this.handleClick.bind(this)
}

render() {
let {content} = this.props
return (

)
}

handleClick(){
let {deleteItem,index} = this.props
deleteItem(index)
}

}

------------------------
propTypes

import PropTypes from 'prop-types'
// 参数校验 / 类型 array,bool,func,number,object,string,symbol,node,element ...
TodoItem.propTypes = {
test:PropTypes.string.isRequired, // 必填
content: PropTypes.string,
deleteItem:PropTypes.func,
index: PropTypes.oneOfType([PropTypes.number,PropTypes.string]) // 既可以是数字 也可以是字符串
}

{this.props.test}
TodoItem.defaultProps = {
test:'hello-word'
}

--------------

ref 使用方法
ref = {(input)=>{this.input = input}
const inputValue =this.input.value;

ref={ul => {this.ul = ul}}
console.log(this.ul.querySelectorAll('div').length);
-------------------
生命周期函数

// 避免子组件被重复调用， 只有参数发生改变才调用
shouldComponentUpdate(nextProps,nextState){
if(nextProps.content !== this.props.content){
return true;
}else{
return false;
}
}

---------------
yarn add axios
res
this.setState(()=>({
list:[...res.data]
}))

-----------------
原生的动画

/* .show{
opacity: 1;
transition: all 1s ease-in;
} */

/* .hide{
opacity: 0;
transition: all 1s ease-in;
} */

@keyframes hide-item {
0%{
opacity: 1;
color: red;
}
50%{
opacity: 0.5;
color: green;
}
100%{
opacity: 0;
color: blue;
}
}

@keyframes show-item {
0%{
opacity: 0;
color: blue;
}
50%{
opacity: 0.5;
color: green;
}
100%{
opacity: 1;
color: red;
}
}

.hide{
animation: hide-item 2s ease-in forwards;
}

.show{
animation: show-item 2s ease-in forwards;
}

----------CSSTransition 动画---------------
yarn add react-transition-group
import {CSSTransition} from 'react-transition-group'

in={this.state.show}
timeout={1000}
classNames="fade"
// 隐藏时 卸载当前dom
unmountOnExit
// 动画结束的钩子函数
onEntered={el=>el.style.color="blue"}
// 第一次加载也有动画
appear={true}
>

toggle

css
.fade-enter, .fade-appear {
opacity: 0;
}

.fade-enter-active, .fade-appear-active{
opacity: 1;
transition: opacity 1s ease-in;
}

.fade-enter-done {
opacity: 1;
color: red;
}

.fade-exit{
opacity: 1;
}

.fade-exit-active{
opacity: 0;
transition: opacity 1s ease-in;
}

.fade-exit-done {
opacity: 0;
}

--------------TransitionGroup 多个item 动画效果------------------------------
render() {
return (


{
this.state.list.map((item,index)=>{
return (
// 隐藏时 卸载当前dom
unmountOnExit
// 动画结束的钩子函数
onEntered={el=>el.style.color="blue"}
// 第一次加载也有动画
appear={true} key={item} >

)
})
}


toggle

)
}

handleAddItem(){
this.setState(prevState =>({
list: [...prevState.list,'item-' + (prevState.list.length + 1)]
}))
}

---------------------------
yarn add antd
-------------
yarn add redux
------------------

yarn add redux-thunk ->可以发送异步请求, 把方法放到 store 里面的actionCreators 里面 操作
1 安装引入 配置
import {createStore,applyMiddleware,compose } from 'redux'
import reducer from './reducer'
import thunk from 'redux-thunk'

const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__({trace:true}) || compose
const enhancer = composeEnhancers(applyMiddleware(thunk))
const strore = createStore(
reducer,
enhancer
);

export default strore

2 写方法 发送异步请求
export const initListAction = (data) =>{
return {
type: INIT_LIST_ACTION,
data
}
}

export const getTodoList = () => {
return (dispatch) => {
axios.get('/list.json').then((res)=>{
const data = res.data;
// 拿到结果 改变列表数据
const action = initListAction(data)
dispatch(action)
})
}
}

3 页面加载 触发请求操作
componentDidMount(){
const action = getTodoList()
store.dispatch(action)
}

---------------------
yarn add redux-saga

1 安装引入 配置

import {createStore,compose,applyMiddleware } from 'redux'
import reducer from './reducer'
import createSagaMiddleware from 'redux-saga'
import TodoSagas from './sagas'

const sagaMiddleware = createSagaMiddleware()
const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__({trace:true}) || compose
const enhancer = composeEnhancers(applyMiddleware(sagaMiddleware))
const strore = createStore(reducer,enhancer);

sagaMiddleware.run(TodoSagas)

export default strore

2 sagas.js

import {takeEvery,put} from 'redux-saga/effects'
import axios from 'axios'

import {
GET_INIT_LIST
} from './actionTypes'

import {
initListAction
} from './actionCreators'

function* getInitList(){

try {
const res = yield axios.get('/list.json')
const action = initListAction(res.data)
yield put(action);
}catch(e){
console.log('list 网络请求失败');
}
}

function* mySaga() {
yield takeEvery(GET_INIT_LIST, getInitList);
}
export default mySaga;

3 actionCreators.js

export const initListAction = (data) =>{
return {
type: INIT_LIST_ACTION,
data
}
}

export const getInitListAction = () => {
return {
type: GET_INIT_LIST
}
}

4 页面使用
componentDidMount(){
const action = getInitListAction()
store.dispatch(action)
}

----------------

yarn add react-redux

1
import { createStore } from 'redux'
import reducer from './reducer'
const store = createStore(
reducer,
window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ && window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__()
)

export default store

import React from 'react';
import ReactDOM from 'react-dom';
import TodoList from './TodoList';
import {Provider} from 'react-redux'
import store from './store';

const App = (



)

ReactDOM.render(App,document.getElementById('root'));

const defaultState = {
inputValue:'hello wrold',
list:[]
}

export default function reducre(state = defaultState,action){
if(action.type === 'change_input_value'){
const newState = JSON.parse(JSON.stringify(state))
newState.inputValue = action.value
return newState
}
return state
}

import React, { Component } from 'react'
import {connect} from 'react-redux'

class TodoList extends Component {

render() {
return (

)
}

}

const mapStateToProps = (state) =>{
return {
inputValue:state.inputValue,
list:state.list
}
}

const mapDispatchToProps = (dispatch) => {
return {
changeInputValue(e){

// console.log(e.target.value);
const action = {
type:"change_input_value",
value:e.target.value
}
dispatch(action)
}
}
}

export default connect(mapStateToProps,mapDispatchToProps)(TodoList)

------------------