function ScrollSetTop(jqueryObj, fClass) {
    if (typeof ScrollSetTop.default === "undefined")
        ScrollSetTop.default = { topArr: [], top: 0 };
    var defalutSetting = ScrollSetTop.default;
    var topArr = defalutSetting.topArr;
    if (typeof fClass === "undefined")
        fClass = "fixedtop";
    var s = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0;
    return setTop(jqueryObj, s);

    function contains(arr, obj) {
        var i = arr.length;
        while (i--) {
            if (arr[i][0] === obj) {
                return i;
            }
        }
        return -1;
    }
    function setTop(obj, s) {
        var i = contains(topArr, obj);
        var top = defalutSetting.top;
        if (i < 0) {
            var objTop = obj.offset().top;
            if (s + top > objTop) {
                var nObj = obj.clone(true);
                nObj.addClass(fClass);
                obj.after(nObj);
                topArr.push([obj, objTop - top, nObj]);
                defalutSetting.top += nObj.height();
                return nObj;
            }
        }
        else if (i == topArr.length - 1) {
            var onetop = topArr[i];
            if (s <= onetop[1]) {
                var nObj = onetop[2];
                defalutSetting.top -= nObj.height();
                nObj.remove();
                topArr.pop();
            }
        }
    }
}