Promiseベースの簡易ルータ

router.js

const EVENT = (pageID) =>  'register:' + pageID

class Router extends EventEmitter {
  constructor () {
    this.routes = {};
  }

  getController (pageID) {
    return new Promise((resolve, reject) => {
      this.once(EVENT(pageID), function () {
        this.routes[pageID](function () {
          resolve(true);
        });
      });
    });
  }

  selectRoute (pageID) {
    var controller = this.getController(pageID);

    if (this.routes[pageID]) {
      this.emit(EVENT(pageID));
    }

    return controller();
  }

  register (pageID, controller) {
    this.routes[pageID] = controller;
    this.emit(EVENT(pageID));
  }
}