普通DOM fadeOut，然后立即fadeIn

$("#element").fadeOut(500, function() {
    $(this).fadeIn(500);
});

function fadeOut(element, duration, callback) {
    let opacity = 1;
    const timer = setInterval(() => {
        if (opacity <= 0) {
            clearInterval(timer);
            element.style.display = 'none';
            if (callback) callback();
        } else {
            opacity -= 0.1;
            element.style.opacity = opacity;
        }
    }, duration / 10);
}

function fadeIn(element, duration) {
    element.style.display = 'block';
    let opacity = 0;
    const timer = setInterval(() => {
        if (opacity >= 1) {
            clearInterval(timer);
        } else {
            opacity += 0.1;
            element.style.opacity = opacity;
        }
    }, duration / 10);
}

const element = document.getElementById('element');
fadeOut(element, 500, () => {
    fadeIn(element, 500);
});