code: function(src, time, flag) {
              var item, vkey, tkey, tval;
              time = Util.toInt(time);
              if (src in Util.stack) {
                  item = Util.stack[src], ctime = Util.getTime();
                  if ((item.time + time * 1000) > ctime) {
                      return item;
                  } else {
                      delete Util.stack[src];
                  }
              } else if (flag && Util.support.storage) { // 从localStorage里查询
                  var l = Util.getLocalKey(src);
                  vkey = l.data;
                  tkey = l.time;
                  item = localStorage.getItem(vkey);
                  if (item) {
                      tval = Util.toInt(localStorage.getItem(tkey));
                      if ((tval + time * 1000) > Util.getTime()) {
                          return {
                              data : item,
                              title : localStorage.getItem(l.title)
                          };
                      } else {
                          localStorage.removeItem(vkey);
                          localStorage.removeItem(tkey);
                          localStorage.removeItem(l.title);
                      }
                  }
              }
              return null;
          }
docs: 获取cache