/**
 * 跳转到指定元素的位置
 * 使用方法
 * scroller(el, duration)
 * el : 目标锚点 ID
 * duration : 持续时间,以毫秒为单位,越小越快
 */
var flutil = {
    intval: function(v) {
        v = parseInt(v);
        return isNaN(v) ? 0 : v;
    },
    getPos: function(e) { // 获取元素信息 
        var l = 0;
        var t = 0;
        var w = this.intval(e.style.width);
        var h = this.intval(e.style.height);
        var wb = e.offsetWidth;
        var hb = e.offsetHeight;
        while (e.offsetParent) {
            l += e.offsetLeft + (e.currentStyle ? this.intval(e.currentStyle.borderLeftWidth) : 0);
            t += e.offsetTop + (e.currentStyle ? this.intval(e.currentStyle.borderTopWidth) : 0);
            e = e.offsetParent;
        }
        l += e.offsetLeft + (e.currentStyle ? this.intval(e.currentStyle.borderLeftWidth) : 0);
        t += e.offsetTop + (e.currentStyle ? this.intval(e.currentStyle.borderTopWidth) : 0);
        return {
            x: l,
            y: t,
            w: w,
            h: h,
            wb: wb,
            hb: hb
        };
    },
    getScroll: function() { // 获取滚动条信息 
        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
        };
    },
    scroller: function(el, duration) { // 锚点(Anchor)间平滑跳转 
        if (typeof el != 'object') {
            el = document.getElementById(el);
        }
        if (!el) return;
        var z = this;
        z.el = el;
        z.p = this.getPos(el);
        z.s = this.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);
    }
}
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