Flickering during scroll restoration with scrollPositionRestoration: 'enabled' in Angular about angular HOT 4 CLOSED

import { ViewportScroller, Location } from '@angular/common';
import { Injectable } from '@angular/core';
import { NavigationStart, Router } from '@angular/router';
import { filter } from 'rxjs/operators';

@Injectable({
    providedIn: 'root'
})
export class RouterScrollService {
    // Scroll positions
    private scrollPositions = new Map();

    //
    // Constructor

    constructor(
        private router: Router,
        private viewportScroller: ViewportScroller,
        private location: Location
    ) {
        // Subscribe to router events

        this.router.events
            .pipe(filter((event) => event instanceof NavigationStart))
            .subscribe((event: any) => {
                if (event.navigationTrigger === 'imperative') {
                    // Get current scroll position
                    const currentScrollPosition = this.viewportScroller.getScrollPosition();

                    // Get current url
                    const currentUrl = this.location.path();

                    // Scroll to the top
                    this.viewportScroller.scrollToPosition([0, 0]);

                    // Get current navigation object
                    const navObject = this.router.getCurrentNavigation();

                    // If the navigation is done with (NavigationExtras) replaceUrl: true
                    if (navObject?.extras.replaceUrl) {
                        this.scrollPositions.set(event.url, currentScrollPosition);

                        this.scrollPositions.delete(currentUrl);
                    }

                    // If the navigation is normal
                    else {
                        // Save the url and scroll position
                        this.scrollPositions.set(currentUrl, currentScrollPosition);
                    }
                } else if (event.navigationTrigger === 'popstate') {
                    // If scroll position is saved

                    if (this.scrollPositions.has(event.url)) {
                        // Scroll to the saved scroll position
                        this.viewportScroller.scrollToPosition(this.scrollPositions.get(event.url));
                    } else {
                        // Scroll to the top
                        this.viewportScroller.scrollToPosition([0, 0]);
                    }
                }
            });
    }
}