參考 1. [topbar/jsaction](https://github.com/ccc111b/html2denojs/tree/master/01-%E5%89%8D%E7%AB%AF/11-app/dropdown/03-jsaction) 2. [dom/navbar2](https://github.com/ccc111b/html2denojs/tree/master/01-%E5%89%8D%E7%AB%AF/04-dom/03-navbar2)
