code: function(routeExp, name, handler) {
          if (utils.isFunction(routeExp)) {
              handler = routeExp;
              routeExp = null;
              name = null;
          }
          if (utils.isFunction(name)) {
              handler = name;
              name = null;
          }
          if (!utils.isFunction(handler)) {
              throw new Error(utils.format('The handler requires function type but got {0} type', utils.type(handler)));
          } else {
              this._handlers.push({
                  name: name, handler: handler,
                  routeExp: (routeExp || '/') // default routeExp to '/'
              });
          }
      }
docs: /*
  register(handler)
  register(routeExp, handler)
  register(routeExp, name, handler)