13.js

function scrollIn() {
    const sliderImages = document.querySelectorAll(".slide-in");
    function checkSlider(e) {
        sliderImages.forEach((sliderImage) => {
            const slideInAt =
                window.scrollY + window.innerHeight - sliderImage.height / 2;
            const imageBottom = sliderImage.offsetTop + sliderImage.height;
            const isHalifShown = slideInAt > sliderImage.offsetTop;
            const isNotScrollPast = window.scrollY < imageBottom;
            if (isHalifShown && isNotScrollPast) {
                sliderImage.classList.add("active");
            } else {
                sliderImage.classList.remove("active");
            }
        });
    }
    document.addEventListener("scroll", checkSlider);
}
window.addEventListener("DOMContentLoaded", scrollIn);