docs: function () {
              if (typeof window !== "undefined") {
  
                  if (this.$.useState) {
                      if (window.removeEventListener) {
                          window.removeEventListener('popstate', this.$checkUrlFn, false);
                      } else {
                          window.detachEvent('onpopstate', this.$checkUrlFn);
                      }
                  } else {
                      if ("onhashchange" in window) {
                          if (window.removeEventListener) {
                              window.removeEventListener('hashchange', this.$checkUrlFn, false);
                          } else {
                              window.detachEvent('onhashchange', this.$checkUrlFn);
                          }
                      } else {
                          // polling
                          clearInterval(this.$checkUrlInterval);
                      }
                  }
              }
          }