gallery.js

function myFunction(imgs) {
    // Get the expanded image
    var expandImg = document.getElementById("expandedImg");
    // Get the image text
    var imgText = document.getElementById("imgtext");
    // Use the same src in the expanded image as the image being clicked on from the grid
    expandImg.src = imgs.src;
    // Use the value of the alt attribute of the clickable image as text inside the expanded image
    imgText.innerHTML = imgs.alt;
    // Show the container element (hidden with CSS)
    expandImg.parentElement.style.display = "block";
  }

  //top button

let mybutton = document.getElementById("myBtn");

// When the user scrolls down 20px from the top of the document, show the button
window.onscroll = function() {scrollFunction()};

function scrollFunction() {
  if (document.body.scrollTop > 20 || document.documentElement.scrollTop > 20) {
    mybutton.style.display = "block";
  } else {
    mybutton.style.display = "none";
  }
}

// When the user clicks on the button, scroll to the top of the document
function topFunction() {
  document.body.scrollTop = 0;
  document.documentElement.scrollTop = 0;
}