$(function () {

        $(".sticky").hide();

        var top = $(window).scrollTop();

        if (top >= 100) {

            $(".sticky").show();

        }

        else {

            $(".sticky").hide();

        }

        $(window).scroll(function () {

            var scrollTop = $(this).scrollTop();

            if (scrollTop >= 100) {

                $(".sticky").show();

            }

            else {

                $(".sticky").hide();

            }

        });

    });

    function backTop() {

        $('body,html').animate({ scrollTop: 0 }, 1000);

    }

window.onload = function () {

    var topbtn = document.getElementById("btn");

    var timer = null;

    var pagelookheight = document.documentElement.clientHeight;

    window.onscroll = function(){

        var backtop = document.body.scrollTop;

        if(backtop >= pagelookheight){

            topbtn.style.display = "block";

        }else{

            topbtn.style.display = "none";

        }

    }

    topbtn.onclick = function () {

        timer = setInterval(function () {

            var backtop = document.body.scrollTop;

            var speedtop = backtop/5;

            document.body.scrollTop = backtop -speedtop;

            if(backtop ==0){

                clearInterval(timer);

            }

        }, 30);

    }

}