按钮滚动到指定位置(JS)

function intval(v) {
    v = parseInt(v);
    return isNaN(v) ? 0 : v;
}
function getPos(e) {
    var l = 0;
    var t = 0;
    var w = intval(e.style.width);
    var h = intval(e.style.height);
    var wb = e.offsetWidth;
    var hb = e.offsetHeight;
    while (e.offsetParent) {
        l += e.offsetLeft + (e.currentStyle ? intval(e.currentStyle.borderLeftWidth) : 0);
        t += e.offsetTop + (e.currentStyle ? intval(e.currentStyle.borderTopWidth) : 0);
        e = e.offsetParent;
    }
    l += e.offsetLeft + (e.currentStyle ? intval(e.currentStyle.borderLeftWidth) : 0);
    t += e.offsetTop + (e.currentStyle ? intval(e.currentStyle.borderTopWidth) : 0);
    return {
        x: l,
        y: t,
        w: w,
        h: h,
        wb: wb,
        hb: hb
    };
}
function getScroll() {
    var t, l, w, h;
    if (document.documentElement && document.documentElement.scrollTop) {
        t = document.documentElement.scrollTop;
        l = document.documentElement.scrollLeft;
        w = document.documentElement.scrollWidth;
        h = document.documentElement.scrollHeight;
    } else if (document.body) {
        t = document.body.scrollTop;
        l = document.body.scrollLeft;
        w = document.body.scrollWidth;
        h = document.body.scrollHeight;
    }
    return {
        t: t,
        l: l,
        w: w,
        h: h
    };
}
function scroller(el, duration) {
    if (typeof el != "object") {
        el = document.getElementById(el);
    }
    if (!el) return;
    var z = this;
    z.el = el;
    z.p = getPos(el);
    z.s = getScroll();
    z.clear = function() {
        window.clearInterval(z.timer);
        z.timer = null
    };
    z.t = (new Date).getTime();
    z.step = function() {
        var t = (new Date).getTime();
        var p = (t - z.t) / duration;
        if (t >= duration + z.t) {
            z.clear();
            window.setTimeout(function() {
                z.scroll(z.p.y, z.p.x)
            }, 13);
        } else {
            st = ((-Math.cos(p * Math.PI) / 2) + 0.5) * (z.p.y - z.s.t) + z.s.t;
            sl = ((-Math.cos(p * Math.PI) / 2) + 0.5) * (z.p.x - z.s.l) + z.s.l;
            z.scroll(st, sl);
        }
    };
    z.scroll = function(t, l) {
        window.scrollTo(l, t)
    };
    z.timer = window.setInterval(function() {
        z.step();
    }, 13);
}

调用方式 ：

onclick="scroller('igbook', 200)"