main.js

// Get the button
var mybutton = document.getElementById("btn-scroll-to-top");

// When the user scrolls down 50px from the top of the document, show the button
window.onscroll = function () {
  scrollFunction();
};

function scrollFunction() {
  if (document.body.scrollTop > 50 || document.documentElement.scrollTop > 50) {
    mybutton.style.display = "block";
  } else {
    mybutton.style.display = "none";
  }
}
// When the user clicks on the button, scroll to the top of the document
mybutton.addEventListener("click", scrollToTop);

function scrollToTop() {
  document.body.scrollTop = 0;
  document.documentElement.scrollTop = 0;
}

function toggleModal(modal_id) {
  document.getElementById(modal_id).classList.toggle("hidden");
}