setTimeout 后在 useEffect 钩子中丢失 ref

Question

I'm trying to play an animation if requested by the prop after mounting the component. But my ref seems to be getting reset to null after a setTimeout.

    let landingText = useRef(null);

    useEffect(() => {
    //ref shows div element here
        setTimeout(() => {
        //ref gets reset to null here
            if (!onShow) {
                playAnimation();
            }
        }, 1000);
    }, []);

I have fixed this by adding a new variable and passing it down -

    useEffect(() => {
        const el = landingText;
        setTimeout(() => {

But I was curious as to why this would be happening after a setTimeout.

Answer 1

发生这种情况的原因是在useEffect的第二个参数中， useEffect只需将空数组[]放在useEffect的第二个参数中，它应该添加onShow