How do I access route parameters?

Dynamic segments

export const appRoutes: Routes = {
  '/posts/:id': () => new PostView(),      // required segment
  '/users/:id?': () => new UsersView(),    // optional segment, must be trailing
};

/posts/:id matches /posts/123 but not /posts. /users/:id? matches both /users and /users/123 — an unmatched optional param is simply absent from the params object, not present with an undefined value.

Reading params inside a view

export class PostView extends View {
  protected onBeforeRender(): void {
    const id = this.getRouteParam('id');
    // ...
  }
}

public getRouteParams(): Record<string, string>       // shallow copy of all matched params
public getRouteParam(key: string): string | undefined
public hasRouteParam(key: string): boolean             // use this to check presence of an optional param

The router calls view.setRouteParams(params) before render() and onEnter() — so route params are always available inside onBeforeRender(), generateTemplate(), and onEnter().