code: function(callback){
      var cssname = 'layer', ver = ''
      ,path = (isLayui ? 'modules/layer/' : 'theme/') + 'default/layer.css?v='+ layer.v + ver;
      isLayui ? layui.addcss(path, callback, cssname) : ready.link(path, callback, cssname);
      return this;
    }
docs: 主体CSS等待事件