阿里前端一面必会 react 面试题总结

import PropTypes from 'prop-types';
class Greeting extends React.Component {  render() {    return (      <h1>Hello, {this.props.name}</h1>    );  }}
Greeting.propTypes = {  name: PropTypes.string};

import React, { Component } from 'react';import { is, fromJS } from 'immutable';import ReactDOM from 'react-dom';import ReactCSSTransitionGroup from 'react-addons-css-transition-group';import './dialog.css';let defaultState = {  alertStatus:false,  alertTip:"提示",  closeDialog:function(){},  childs:''}class Dialog extends Component{  state = {    ...defaultState  };  // css动画组件设置为目标组件  FirstChild = props => {    const childrenArray = React.Children.toArray(props.children);    return childrenArray[0] || null;  }  //打开弹窗  open =(options)=>{    options = options || {};    options.alertStatus = true;    var props = options.props || {};    var childs = this.renderChildren(props,options.childrens) || '';    console.log(childs);    this.setState({      ...defaultState,      ...options,      childs    })  }  //关闭弹窗  close(){    this.state.closeDialog();    this.setState({      ...defaultState    })  }  renderChildren(props,childrens) {    //遍历所有子组件    var childs = [];    childrens = childrens || [];    var ps = {        ...props,  //给子组件绑定props        _close:this.close  //给子组件也绑定一个关闭弹窗的事件           };    childrens.forEach((currentItem,index) => {        childs.push(React.createElement(            currentItem,            {                ...ps,                key:index            }        ));    })    return childs;  }  shouldComponentUpdate(nextProps, nextState){    return !is(fromJS(this.props), fromJS(nextProps)) || !is(fromJS(this.state), fromJS(nextState))  }     render(){    return (      <ReactCSSTransitionGroup        component={this.FirstChild}        transitionName='hide'        transitionEnterTimeout={300}        transitionLeaveTimeout={300}>        <div className="dialog-con" style={this.state.alertStatus? {display:'block'}:{display:'none'}}>            {this.state.childs}        </div>      </ReactCSSTransitionGroup>    );  }}let div = document.createElement('div');let props = {   };document.body.appendChild(div);let Box = ReactD

//子类jsximport React, { Component } from 'react';class Child extends Component {    constructor(props){        super(props);        this.state = {date: new Date()};  }  showValue=()=>{    this.props.showValue && this.props.showValue()  }  render() {    return (      <div className="Child">        <div className="content">           Child           <button onClick={this.showValue}>调用父的方法</button>        </div>      </div>    );  }}export default Child;

.dialog-con{    position: fixed;    top: 0;    left: 0;    width: 100%;    height: 100%;    background: rgba(0, 0, 0, 0.3);}

import React from 'react';function ExampleApplication() {  return (    <div>      <Header />      <React.StrictMode>                <div>          <ComponentOne />          <ComponentTwo />        </div>      </React.StrictMode>            <Footer />    </div>  );}

class App extends Component {  constructor(props) {    super(props);    this.state = {      username: "有课前端网",      msg: " ",    };  }  render() {    return <div> {this.state.msg}</div>;  }  componentDidMount() {    this.setState((oldState, props) => {      return {        msg: oldState.username + " - " + props.intro,      };    });  }}

import React,{Component} from 'react';import ReactDOM from 'react-dom';import PropTypes from 'prop-types';class Header extends Component{    render() {        return (            <div>                <Title/>            </div>        )    }}class Title extends Component{    static contextTypes={        color:PropTypes.string    }    render() {        return (            <div style={{color:this.context.color}}>                Title            </div>        )    }}class Main extends Component{    render() {        return (            <div>                <Content>                </Content>            </div>        )    }}class Content extends Component{    static contextTypes={        color: PropTypes.string,        changeColor:PropTypes.func    }    render() {        return (            <div style={{color:this.context.color}}>                Content                <button onClick={()=>this.context.changeColor('green')}>绿色</button>                <button onClick={()=>this.context.changeColor('orange')}>橙色</button>            </div>        )    }}class Page extends Component{    constructor() {        super();        this.state={color:'red'};    }    static childContextTypes={        color: PropTypes.string,        changeColor:PropTypes.func    }    getChildContext() {        return {            color: this.state.color,            changeColor:(color)=>{                this.setState({color})            }        }    }    render() {        return (            <div>                <Header/>                <Main/>            </div>        )    }}ReactDOM.render(<Page/>,document.querySelector('#root'));

class NewsList extends Component {  componentDidMount () {     this.fetchData(this.props.location);  }
  fetchData(location) {    const type = location.pathname.replace('/', '') || 'top'    this.props.dispatch(fetchListData(type))  }  componentWillReceiveProps(nextProps) {     if (nextProps.location.pathname != this.props.location.pathname) {         this.fetchData(nextProps.location);     }   }  render () {    ...  }}

<Icketang username="雨夜清荷">{(user) => (user ? <Info user={user} /> : <Loading />)}</Icketang>;import React, { Component } from "react";export class Icketang extends Component {  //请实现你的代码}

import React, { Component } from "react";class Icketang extends Component {  constructor(props) {    super(props);    this.state = {      user: props.user,    };  }  componentDidMount() {    //模拟异步获取数据操作，更新状态    setTimeout(      () =>        this.setstate({          user: "有课前端网",        }),      2000    );  }  render() {    return this.props.children(this.state.user);  }}class Loading extends Component {  render() {    return <p>Loading.</p>;  }}class Info extends Component {  render() {    return <h1> {this.props.user}</h1>;  }}

import { render } from "react-dom";render(<Icketang>{(user) => (user ? <Info user={user} /> : <Loading />)}</Icketang>, ickt);

render(<Icketang user="雨夜清荷">{(user) => (user ? <Info user={user} /> : <Loading />)}</Icketang>, ickt);