var menu = function () {
    var t = 15,
		z = 50,
		s = 6,
		a;

    function dd(n) {
        this.n = n;
        this.h = []; // 存取有子菜单的项目
        this.c = []	 // 存取子菜单
    }
    dd.prototype = {
        init: function (p, c) {
            a = c;
            var w = document.getElementById(p),
				s = w.getElementsByTagName('ul'),
				l = s.length, //二级菜单的个数
				i = 0;

            for (i; i < l; i++) {
                var h = s[i].parentNode;
                this.h[i] = h;
                this.c[i] = s[i];

                h.onmouseover = new Function(this.n + '.st(' + i + ',true)');
                h.onmouseout = new Function(this.n + '.st(' + i + ')');
            }
        },

        st: function (x, f) {
            var c = this.c[x],
				h = this.h[x],
				p = h.getElementsByTagName('a')[0];

            clearInterval(c.t);
            c.style['overflow'] = 'hidden';

            if (f) {
                p.className += ' ' + a;
                if (!c.mh) {
                    c.style.display = 'block';
                    c.style.height = '';
                    c.mh = c.offsetHeight;
                    c.style.height = 0;
                }

                if (c.mh == c.offsetHeight) {
                    c.style.overflow = 'visible';
                } else {
                    c.style.zIndex = z;
                    z++;
                    c.t = setInterval(function () { sl(c, 1) }, t);
                }

            } else {
                p.className = p.className.replace(a, '');
                c.t = setInterval(function () { sl(c, -1) }, t);
            }


        }
    }

    function sl(c, f) {
        var h = c.offsetHeight;
        if ((h <= 0 && f != 1) || (h >= c.mh && f == 1)) {
            if (f == 1) {
                c.style.filter = '';
                c.style.opacity = 1;
                c.style.overflow = 'visible';
            }
            clearInterval(c.t); return
        }
        var d = (f == 1) ? Math.ceil((c.mh - h) / s) : Math.ceil(h / s), o = h / c.mh;
        c.style.opacity = o;
        c.style.filter = 'alpha(opacity=' + (o * 100) + ')';
        c.style.height = h + (d * f) + 'px';
    }

    return { dd: dd };

} ();