Custom scroll position restoration logic for Angular 2+, that doesn't consider query parameter changes in route as forward navigation, thus preventing certain scenarios where you don't want query parameter changes to scroll-to-top as they would with 'scrollPositionRestoration: enabled'.

better-scroll-restoration-logic-angular.ts

export class AppModule {
  constructor(private router: Router, private viewportScroller: ViewportScroller) {
    // Disable automatic scroll restoration to avoid race conditions
    this.viewportScroller.setHistoryScrollRestoration('manual');
    
    this.handleScrollOnNavigation();
  }

  /**
   * When route is changed, Angular interprets a simple query params change as "forward navigation" too.
   * Using the pairwise function allows us to have both the previous and current router events, which we can
   * use to effectively compare the two navigation events and see if they actually change route, or only
   * the route parameters (i.e. selections stored in query params).
   *
   * Related to: https://github.com/angular/angular/issues/26744
   */
  private handleScrollOnNavigation(): void {
    this.router.events.pipe(
      // import { Event } from '@angular/router'
      filter((e: Event): e is Scroll => e instanceof Scroll),
      pairwise()
    ).subscribe((e: Scroll[]) => {
      const previous = e[0];
      const current = e[1];
      if (current.position) {
        // Backward navigation
        this.viewportScroller.scrollToPosition(current.position);
      } else if (current.anchor) {
        // Anchor navigation
        this.viewportScroller.scrollToAnchor(current.anchor);
      } else {
        // Check if routes match, or if it is only a query param change
        if (this.getBaseRoute(previous.routerEvent.urlAfterRedirects) !== this.getBaseRoute(current.routerEvent.urlAfterRedirects)) {
          // Routes don't match, this is actual forward navigation
          // Default behavior: scroll to top
          this.viewportScroller.scrollToPosition([0, 0]);
        }
      }
    });
  }

  private getBaseRoute(url: string): string {
    // return url without query params
    return url.split('?')[0];
  }
}

Thanks!

thanks! but I have one question. is it ok to not unsubscribe from this subscription in case of just frontend app / in case of the app with server-side rendering?

It is also working for me, thanks!
I have one more improvement. Add the following line before calling this.handleScrollOnNavigation();

this.viewportScroller.setHistoryScrollRestoration('manual');

This way automatic scrolling from browser will be turned off so there are no scrolling results race conditions. In my case on navigating back I first saw scroll to top even before route change and before this.viewportScroller.scrollToPosition(current.position); was called,

@anbaran Thanks, updated code to reflect this.

👍

This may have been obvious to others but it wasn't to me. I had to change our app's router settings for scrollPositionRestoration to:
{ scrollPositionRestoration: 'disabled' } to get this workaround to work.

It took me a bit to figure that out. So if you are also wondering why this doesn't seem to work for you, check and make sure that is disabled.