问React记忆异步回调中的值

EN

function App() {
    const [val, setVal] = React.useState(42)

    const handleHide = () => {
        setVal(null)
    }

    const handleDisplay = () => {
        setTimeout(() => {
            alert(val)
        }, 3000)
    }

    return (
        <div>
            <p>VAL: {val ? val : 'null'}</p>
            <button onClick={handleDisplay}>[1] display value with delay</button>
            <button onClick={handleHide}>[2] hide immediately</button>
        </div>
    )
}