squirrel/static/js/totop.js

const scrollToTopButton = document.getElementById('totop');
const scrollToTopListener = () => {
    if (window.scrollY > 0) {
        scrollToTopButton.className = "button fab show";
    } else {
        scrollToTopButton.className = "button fab hide";
    }
};

window.addEventListener("scroll", scrollToTopListener);