The most minimalist way to inlude smooth scroll in JQuery after an on_click event is triggered. I specifically integrated this in my website.

JQuery

function go_top() {
window.scrollTo({ 
    top: 0, 
    behavior: 'smooth' });   
}
function go_bottom() {
window.scrollTo({ 
    top: document.body.scrollHeight, 
    behavior: 'smooth' }); 
}

HTML

<a onclick="go_top()">Back to top</a>
<a onclick="go_bottom()">Go to bottom</a>

See a demo here