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);
}

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