jQuery插件实现控制网页元素动态居中显示

(function($){  $.fn._center = function(self, parent, dimension)  {    if(!dimension.vertical && !dimension.horizontal)      return; //won't do anything anyway    if(parent)      parent = self.parent();    else      parent = window    self.css("position", "absolute");    if(dimension.vertical)    {      self.css("top", Math.max(0, (($(parent).height() - $(self).outerHeight()) / 2) + $(parent).scrollTop()) + "px");    }    if(dimension.horizontal)    {      self.css("left", Math.max(0, (($(parent).width() - $(self).outerWidth()) / 2) + $(parent).scrollLeft()) + "px");    }    return self;  };  $.fn.center = function(parent, args)  {    if(!args)    {      args = {horizontal: true, vertical: true};    }    return this.each(function()    {      var obj = $(this);      obj._center(obj, parent, args);      function callback()      {        obj._center(obj, parent, args);      }      callback();      $(window).resize(callback);    });  };})(jQuery);