goTop - pulsante torna su #gotop #up #js #button

css.css

.goUp {
    position: fixed;
    right: 20px;
    bottom: 20px;
    font-size: 30px;
    color: $blue;
    padding: 0 9.3px;
    z-index: 999;
    background-color: rgba(0, 0, 0, .3);
    -webkit-border-radius: 8px;
    -moz-border-radius: 8px;
    border-radius: 8px;
    display: none;
}

html.html

<!-- nel footer uso font awesome 5 -->

<a class="goUp scroll" href="#top"><i class="fas fa-chevron-up"></i></a>

script.js

$(document).scroll(function() {
  var y = $(this).scrollTop();
  if (y > 500) {
    $('.goUp').fadeIn();
  } else {
    $('.goUp').fadeOut();
  }
});

$(".scroll").click(function(event){

        var offset = 230; //offset rispetto a posizione dell'ancora  
        //customizzo offset con un attributo data il link 
        if($(this).data('offset')) {
          offset = $(this).data('offset');
        }
        
        //prevent the default action for the click event
        event.preventDefault();
  
        //get the full url - like mysitecom/index.htm#home
        var full_url = this.href;
  
        //split the url by # and get the anchor target name - home in mysitecom/index.htm#home
        var parts = full_url.split("#");
        var trgt = parts[1];
  
        //get the top offset of the target anchor
        var target_offset = $("#"+trgt).offset();
        var target_top = target_offset.top;
  
        //goto that anchor by setting the body scroll top to anchor top
        $('html, body').animate({scrollTop:target_top - offset}, 1500);
    });