scrollToBottom.js

var Scroller = (function() {
    var scrollHandle = 0;
    var height = () => {
        var body = document.body, html = document.documentElement;
        var height = Math.max( body.scrollHeight, body.offsetHeight, html.clientHeight, html.scrollHeight,html.offsetHeight );
        return height;
    };

    var slowScroll = (amt) => {
        window.scrollBy({left: 0, top: amt, behavior: 'smooth'});
    };

    var scrollBottom = (defaultAmount, defaultPeriod) => {
       var amt = defaultAmount || 250;
       var period = defaultPeriod || 80;
       var lengths = height() / amt;
       scrollHandle = window.setInterval(() => {slowScroll(amt)}, period);
       window.setTimeout(() => {window.clearInterval(scrollHandle);}, period * lengths);
    };

    var stopScroll = () => {
        window.clearInterval(scrollHandle);
    };

    return {height, slowScroll, scrollBottom, stopScroll};
})();