返回顶部

function backTop(btnId) {

    var btn = document.getElementById(btnId);

    var d = document.documentElement;

    var b = document.body;

    window.onscroll = set;

    btn.style.display = "none";

    btn.onclick = function() {

        btn.style.display = "none";

        window.onscroll = null;

        this.timer = setInterval(function() {

            d.scrollTop -= Math.ceil((d.scrollTop + b.scrollTop) * 0.1);

            b.scrollTop -= Math.ceil((d.scrollTop + b.scrollTop) * 0.1);

            if ((d.scrollTop + b.scrollTop) == 0) clearInterval(btn.timer, window.onscroll = set);

        },

        10);

    };

    function set() {

        btn.style.display = (d.scrollTop + b.scrollTop > 100) ? 'block': "none"

    }

};

调用：

backTop('goTop');