最基本的一个todolist，涉及基本的组件通信。效果如下：

index.js

import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import TodoList from './TodoList';
import * as serviceWorker from './serviceWorker';

ReactDOM.render(
  <React.StrictMode>
    <TodoList />
  </React.StrictMode>,
  document.getElementById('root')
);

// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();

TodoList.js

import React,{Component,Fragment} from 'react';
import TodoItem from './TodoItem';
import Test from './Test';

class TodoList extends Component{

    // 当组件的state或者props发生改变时，render函数会重新执行
    constructor(props){
        super(props);
        this.state = {
            inputValue:'',
            list:[]
        }
        this.handleInputChange = this.handleInputChange.bind(this);
        this.handleBtnClick = this.handleBtnClick.bind(this);
        this.handleItemDelete = this.handleItemDelete.bind(this);
    }
    componentWillMount(){
        // console.log('componentWillMount');
    }
    render(){
        // console.log('render');
        return (
            <Fragment>
                <div>
                    <label htmlFor="insertArea">输入内容</label>
                    <input
                        id="insertArea"
                        value={this.state.inputValue}
                        onChange={this.handleInputChange}
                        ref={(input)=>{this.input = input}}
                    />
                    <button onClick={this.handleBtnClick}>提交</button>
                </div>
                <ul>
                    {
                        this.getTodoItem()
                    }
                </ul>
                {/* <Test content={this.state.inputValue}/> */}
            </Fragment>
        )
    }

    getTodoItem(){
        return this.state.list.map((item,index)=>{
            return(
                <div key={index}>
                    <TodoItem
                        content = {item}
                        index = {index}
                        deleteItem = {this.handleItemDelete}
                    />
                </div>
            )
        })
    }

    handleInputChange(e){
        // const value = e.target.value; // 使用setState异步函数赋值必须将e.target值提前赋值，不然会报错
        const value = this.input.value;
        this.setState(()=>({
            // inputValue:e.target.value
            inputValue:value
        }));
        
    }

    handleBtnClick(){

        this.setState((prevState)=>({
            list:[...prevState.list,prevState.inputValue], //数组追加元素
            inputValue:''
        }));
    }

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

}
export default TodoList;

TodoItem.js

import React,{Component} from 'react';

class TodoItem extends Component{

    constructor(props){
        super(props);
        this.handleClick = this.handleClick.bind(this);
    }
    shouldComponentUpdate(nextProps,nextState){
        if(nextProps.content !== this.props.content){
            return true;
        }else{
            return false;
        }
    }
    render(){
        console.log('TodoItem render');
        const {content} =  this.props ;
        return(
            <div 
                onClick={this.handleClick}
                dangerouslySetInnerHTML={
   {__html:content}}
            
            />
                
        )
    }

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

}
export default TodoItem;

代码链接：

链接：https://pan.baidu.com/s/1HKikCZontl2wQig1oXKc8Q 
提取码：hghn 
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