classAppextendsReact.Component{state={count:0}handleCountClick=()=>{this.setState({count:this.state.count+1});console.log(this.state.count);}render(){return(the count is{this.state.count})}}ReactDOM.render(<App/>,document.getElementById('container')); count初始值为 0,当我们触发handleCou...
constclassComponentUpdater={isMounted,// inst其实就是组件实例对象的this enqueueSetState(inst, payload, callback) { // 获取当前实例上的fiber const fiber = getInstance(inst); const currentTime = requestCurrentTime(); const expirationTime = computeExpirationForFiber(currentTime, fiber); const update =...
import React from 'react'//类式组件//class Demo extends React.Component {//state = { count: 0 }//myRef = React.createRef()//add = () => {//this.setState({count: this.state.count+1})//}//componentDidMount() {//setInterval(() => {//this.setState(state => ({count: state...
importReactfrom'react';import'./App.css';classAppClassextendsReact.Component{state={count:0,};handleClick=()=>{this.setState({count:1});console.log('count: ',this.state.count);this.setState({count:2});console.log('count: ',this.state.count);setTimeout(()=>{this.setState({count:3...
classComponentextendsReact.Component{constructor(props) {super(props)this.state= {a:1, } } handleClickWithPromise =() =>{Promise.resolve().then(() =>{this.setState({a:this.state.a+1})this.setState({a:this.state.a+1}) })
import React, { Component } from "react" class Comp extends Component { constructor(props) { super(props) this.state = { val: 0 } } componentDidMount() { this.setState({val: this.state.val+1}) console.log(this.state.val) this.setState({val: this.state.val+1}) ...
在组件生命周期或React合成事件中,setState是异步; 在setTimeout或者原生dom事件中,setState是同步; React中其实是通过一个函数来确定的:enqueueSetState部分实现(react-reconciler/ReactFiberClassComponent.js) enqueueSetState(inst, payload, callback) {constfiber = getInstance(inst);// 会根据React上下文计算一个...
import React, { Component } from 'react' export default class App extends Component { constructor(props) { super(props); this.state = { message: "Hello World" } } render() { return ( {this.state.message} this.changeText()}>改变文本 ) } changeText() { } } 关键是changeText...
class Example extends React.Component { constructor(props) { super(props); } state = { value: 0 } render() { return ( The Value: {this.state.value} add Value ); } _addValue() { this.setState({ value: this.state.value
React-组件-setState setState 是如何给 state 赋值的 通过Object.assign() importReactfrom'react'; classHomeextendsReact.Component{ constructor(props) { super(props); this.state={ name:'BNTang', age:18 } letoldObj={name:'BNTang',age:18};...