MediaWiki:Scroll-to-Top.js

/* -- SCROLL TO TOP BUTTON -- */
/* Insert Top Button after Body Content */
$(function() {
  $('<button onclick="topFunction()" id="topBtn" title="Go to top"></button>').insertAfter('div#mw-content-text');
});

// When users scroll down 100px, show the Top button
window.onscroll = function() {scrollFunction()};

function scrollFunction() {
  if (document.body.scrollTop > 100 || document.documentElement.scrollTop > 100) {
    document.getElementById("topBtn").style.display = "block";
  } else {
    document.getElementById("topBtn").style.display = "none";
  }
}

// When users click on Top button, scroll up
function topFunction() {
  document.body.scrollTop = 0;
  document.documentElement.scrollTop = 0;
}