code: function() {
  
          var popup = this.__popup;
          var $window = $(window);
          var $document = $(document);
          var fixed = this.fixed;
          var dl = fixed ? 0 : $document.scrollLeft();
          var dt = fixed ? 0 : $document.scrollTop();
          var ww = $window.width();
          var wh = $window.height();
          var ow = popup.width();
          var oh = popup.height();
          var left = (ww - ow) / 2 + dl;
          var top = (wh - oh) * 382 / 1000 + dt; // 黄金比例
          var style = popup[0].style;
  
  
          style.left = Math.max(parseInt(left), dl) + 'px';
          style.top = Math.max(parseInt(top), dt) + 'px';
      }
docs: 居中浮层