Hi,

Please refer to the code:

const publicWidget = require('web.public.widget');

    publicWidget.registry.ScrollButton = publicWidget.Widget.extend({

        selector: 'body',   // attach to body or a container

        start: function () {

            const button = document.getElementById("IdButton");

            if (!button) {

                return;  // stop if button not on page

            }

            window.addEventListener("scroll", function () {

                let scroll = window.scrollY || document.documentElement.scrollTop;

                if (scroll >= window.innerHeight / 2) {

                    button.classList.add("active");

                } else {

                    button.classList.remove("active");

                }

            });

        },

    });

Hope it helps.

Hello George

Just a suggestion in odoo you can use this as a scroll event

$(document).ready(function () {

    let lastScrollTop = 0;

    const $button = $('#my-button'); // your button selector

    $('#wrapwrap').on('scroll', function () {

        let scrollTop = $('#wrapwrap').scrollTop(),

            windowHeight = $(window).height();

        console.log('Current scrollTop:', scrollTop);

        // Add 'active' class when scroll reaches half window height

        if (scrollTop > windowHeight / 2) {

            $button.addClass('active');

            console.log('Button shown');

        } else {

            $button.removeClass('active');

            console.log('Button hidden');

        }

        lastScrollTop = scrollTop;

    });

});