hooks的使用

useRef

案例效果：

• 点击按钮，文本title修改
• 点击按钮，input聚焦

  import React, { useRef, PureComponent } from 'react'
  
  class TestChild extends PureComponent {
    render() {
      return (
        <div>UseRefDemo</div>
      )
    }
  }
  
  export default function UseRefDemo() {
    const titleRef = useRef()
    const inputRef = useRef()
    const testChild = useRef()
    return (
      <>
      <div>UseRefDemo</div>
      <div ref= {titleRef}>title</div>
      <input ref = {inputRef} type = "text"></input>
      <button onClick={e => changeDom()}>按钮</button>
      <TestChild ref = {testChild}></TestChild>
      </>
    )
  
  function changeDom(){
      titleRef.current.innerHTML = "改变后的title"
      inputRef.current.focus()
      console.log(testChild)
    }
  }