publiclab/plots2

jQuery(document).ready(function() {     
    var duration = 300;

    $(".back-to-top").click(function(event) {
        event.preventDefault();
        jQuery("html, body").animate({scrollTop: 0}, duration);         
        return false;
    })

    let options = {
        root: null,
        threshold: .75
    }
    
    function scrollToTop(entries, observer){
        let scrollToTopBtn = $(".back-to-top");
        entries.forEach(entry => {
            if (entry.isIntersecting) {
                scrollToTopBtn.fadeOut(300)
            } else {
                scrollToTopBtn.fadeIn(300)
            }
        })
    }

    const heading = document.querySelector("h1");

    if(heading !== null) {
        let observer = new IntersectionObserver(scrollToTop, options);
        observer.observe(heading);
    }
});