A simple auto scroller button, can be pasted in browser console or injected in other ways in any website

autoScroller.js

// Simply copy and paste the following script in your browser's console,
// it will add an auto-scrolling button on the right part of the webpage you are visiting.
(function() {
    let cssScrolling = "background-color: #f44336; border: none; color: white; padding: 15px 32px; text-align: center; text-decoration: none; display: inline-block; font-size: 16px;    float:right; position:fixed; right:0; top:50%;";
    let cssStopped = "background-color: #4CAF50; border: none; color: white; padding: 15px 32px; text-align: center; text-decoration: none; display: inline-block; font-size: 16px;    float:right; position:fixed; right:0; top:50%;";

    let btn = document.createElement("button");
    var isScrolling = false;
    btn.innerHTML = "start scroll";
    btn.style.cssText = cssStopped;
        
    let onclick = function() {
        console.log("click");
        isScrolling = !isScrolling;
        autoScroll()
    };
    btn.addEventListener("click", onclick);
    let autoScroll = () => {
        if (isScrolling) {
            window.scrollBy(0, 1);
            btn.innerHTML = "stop scroll";
            btn.style.cssText = cssScrolling;
            setTimeout(autoScroll, 10);
        } else {
            btn.innerHTML = "start scroll";
            btn.style.cssText = cssStopped;
            
        }
    };
    document.body.appendChild(btn);
})();

// It is also possible to create a bookmarklet (a bookmark containing the following code) to obtain the same result
// just clicking on the bookmark
javascript: (function() {let cssScrolling = "background-color: #f44336; border: none; color: white; padding: 15px 32px; text-align: center; text-decoration: none; display: inline-block; font-size: 16px;    float:right; position:fixed; right:0; top:50%;"; let cssStopped = "background-color: #4CAF50; border: none; color: white; padding: 15px 32px; text-align: center; text-decoration: none; display: inline-block; font-size: 16px;    float:right; position:fixed; right:0; top:50%;"; let btn = document.createElement("button"); var isScrolling = false; btn.innerHTML = "start scroll"; btn.style.cssText = cssStopped; let onclick = function() {console.log("click"); isScrolling = !isScrolling; autoScroll() }; btn.addEventListener("click", onclick); let autoScroll = () => {if (isScrolling) {window.scrollBy(0, 1); btn.innerHTML = "stop scroll"; btn.style.cssText = cssScrolling; setTimeout(autoScroll, 10); } else {btn.innerHTML = "start scroll"; btn.style.cssText = cssStopped; } }; document.body.appendChild(btn); })();