react组件中获取DOM元素的五种方式

    <h1 ref="myH1"></h1>
    this.refs.myH1

    this.myH2 = React.createRef() 
    <h2 ref={this.myH2}></h2>
    this.myH2.current

    <h3 ref={ ele => this.myH3 = ele }></h3>
    this.myH3

    const d1 = useRef()
    <div id="d1" ref={d1}>div1</div>
    d1.current

    const d2 = useRef()
    <div id="d2" ref={el => d2=el}>div1</div>
    d2