Js返回顶部的方法

if (window.addEventListener) {
    window.addEventListener('load', goTopEx);
} else if (window.attachEvent) {
    window.attachEvent('onload', goTopEx);
} else {
    window.onload = goTopEx;
}
function goTopEx() {
    var obj = document.getElementById("goTopBtn");
    getScrollTop() > 0 ? obj.style.display = "": obj.style.display = "none";
    function getScrollTop() {
        return document.documentElement.scrollTop + document.body.scrollTop;
    }
    function setScrollTop(value) {
        if (document.documentElement.scrollTop) {
            document.documentElement.scrollTop = value;
        } else {
            document.body.scrollTop = value;
        }
    }
    window.onscroll = function() {
        getScrollTop() > 0 ? obj.style.display = "": obj.style.display = "none";
    }
    obj.onclick = function() {
        var goTop = setInterval(scrollMove, 10);
        function scrollMove() {
            setScrollTop(getScrollTop() / 1.1);
            if (getScrollTop() < 1) clearInterval(goTop);
        }
    }
}

返回顶部的代码