text: import React, { memo, useMemo } from 'react';
  
  function FFunc() {
    const [count, setCuont] = React.useState(1); // eslint-disable-line
    const [name, setName] = React.useState('FFunc');
    console.log('in', 'FFunc');
  
    const handleChangeFunc = () => setName('FF');
  
    // const expensive = () => {
    //   console.log('compute');
    //   return count + 1;
    // }
    const expensive = useMemo(() => {
      console.log('compute');
      return count + 1;
    }, [count]);
  
    // const callback = () => {
    //   console.log(count);
    // }
    // const callback = useCallback(() => {
    //   console.log('callback', count);
    // }, [count]);
    // set.add(callback);
  
  
    return (<div>
      <p>{name}</p>
      <div onClick={handleChangeFunc}>Change FFunc</div>
      <p>{expensive}</p>
    </div>)
  }
  
  export default memo(FFunc);
  