Javascript 实现锚点(Anchor)间平滑跳转

(function($){
    $.fn.scroller = function(options){
        var defaultVal = {
            duration:500
        };
        var obj = $.extend({},defaultVal,options);
        var el = options.el;
        var duration = options.duration;
        return this.each(function(){
            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);
            });
    };
    
    function intval(v)
    {
        v = parseInt(v);
        return isNaN(v) ? 0 : v;
    }
    
    // 获取元素信息
    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};
    }
    // 获取滚动条信息
    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 };
    }
})(jQuery)

$(function(){
    $('#goto').click(function(){
        $(this).scroller(
            {
                el:'t1',
                duration:1000
            }
        );
    });
})