code: function React_root(params) {
      const this_root = this;
      if (!(this_root instanceof React_root)) {
          return new React_root(params);
      }
  
      this_root.routes = VALIDATION.ensure_valid_routes(params.routes);
  
      // Is app root?
      // Meaning, does this React root control top-level navigation,
      // like change the url and the title of the document
      this_root.is_app_root = Boolean(params.is_app_root);
  
      // Props that initialize state (so let the component validate)
      if (!this_root.is_app_root) {
          this_root.url = params.url || null;
          this_root.path = params.path || null;
          this_root.query = params.query || null;
          this_root.fragment = params.fragment || null;
      }
  
      this_root.page = null;
  
      return this_root;
  }
docs: -----------