jquery: 回到顶部

function toggleToTopBtn(toTopBtn, scrollTop, clientHeight) {
            if (scrollTop > clientHeight) {
                toTopBtn.css('display', 'block')
            } else {
                toTopBtn.css('display', 'none')
            }
        }

 $(document).ready(function () {
            /*回到顶部*/
            let toTopBtn = $('#toTopBtn');
            let scrollTop = $(document).scrollTop();
            let clientHeight = document.documentElement.clientHeight;
            toggleToTopBtn(toTopBtn, scrollTop, clientHeight);
            $(window).on('scroll', () => {
                scrollTop = $(document).scrollTop();
                toggleToTopBtn(toTopBtn, scrollTop, clientHeight);
            })
            toTopBtn.on('click', () => {
                $('body,html').animate({
                    scrollTop: 0
                }, 500)
            })
        })