react 基础（useCallback）

useCallback 作用，主要用于缓存函数的。

import { FC, useCallback, useMemo, useState } from 'react';


const UserCallback: FC = () => {
    
    const [text, setText] = useState('hello')
    const fn1 = () => {
        console.log('fn1')
    }
    const fn2 = useCallback(() => {
        console.log('fn2 text', text)
    }, [text])
    return <>
        <div>
            <button onClick={fn1}> fn1</button> 
            <div>
                <button onClick={fn2}> fn2</button>
            </div>
            {text}
            <div>
                <input type="text" value={text} onChange={e => setText(e.target.value) } />
            </div>
        </div>
    </>
}

export default UserCallback;