基础知识 - Hooks ​

import React, { useState, useRef } from "react";
import ReactDom from 'react-dom';
function App() {
  const [Value, setValue] = useState("");
  const MyRef = useRef(null); //创建ref属性实例
  const [num, setnum] = useState(0);

  // 创建一个数据
  const MyRefvalue = useRef(0);
  const handerAdd = () => {
    setnum(num + 1);
    // 修改数据
    MyRefvalue.current++;
  };
  return (
    <div>
      <input
        ref={MyRef}
        value={Value}
        onChange={() => {
          setValue(MyRef.current.value);
        }}
      ></input>
      {Value}

      <div>
        <button onClick={() => handerAdd()}>Add</button>
        {num}- {MyRefvalue.current}
      </div>
    </div>
  );
}

ReactDom.render(<App>,document.getElementById('root'))