react demo1 TodoList

实现增加和删除：

import React, {Component} from 'react';


class TodoList extends Component {


  //使用方法2：
  myRef = React.createRef();

  state = {
    list: [1, 2, 3]
  }

  render() {
    return (
        <div>

          <input type="text" ref={this.myRef}/>


          <button onClick={() => {
            this.handleAdd();
          }}>add
          </button>


          <ul>
            {
              this.state.list.map((item, index) => <li key={item}>
                {/*{item}*/}

                {/*如果要支持富文本识别的话，比较危险*/}
                <span dangerouslySetInnerHTML={{__html: item}}></span>

                <button onClick={() => {
                  this.handleDel(index)
                }}>del
                </button>
              </li>)
            }
          </ul>


          {/*  条件渲染方式1：*/}
          {/*{this.state.list.length === 0 ? 暂无待办事项 : null}*/}

          {/*条件渲染方式2：*/}
          {this.state.list.length === 0 && <div>暂无待办事项</div>}

        </div>
    );

  }


  // 处理添加
  handleAdd = () => {
    console.log('click1', this.myRef.current.value)

    let newList = [...this.state.list];
    newList.push(this.myRef.current.value);
    this.setState({
      list: newList
    })
    this.myRef.current.value = '';
  }

  // 处理删除
  handleDel = (index) => {
    // console.log('del', index)
    let newList = this.state.list.slice();
    newList.splice(index, 1);
    this.setState({
      list: newList,

    })
  }

}

export default TodoList;