React-loadable package -https://github.com/jamiebuilds/react-loadable/blob/6201c5837b212d6244c57f3748f2b1375096beeb/src/index.js#L100

createLoadableComponent

  render() {
      if (this.state.loading || this.state.error) {
        return React.createElement(opts.loading, {
          isLoading: this.state.loading,
          pastDelay: this.state.pastDelay,
          timedOut: this.state.timedOut,
          error: this.state.error,
          retry: this.retry
        });
      } else if (this.state.loaded) {
        return opts.render(this.state.loaded, this.props);
      } else {
        return null;
      }