Routing Interceptor for Angular7

ng-routing.interceptor.ts

import { Router, NavigationStart } from '@angular/router';
import { filter, pairwise } from 'rxjs/operators';


export function parseQuery(queryString: string) {
  const query = {};
  const pairs = (queryString[0] === '?' ? queryString.substr(1) : queryString).split('&');
  for (let i = 0; i < pairs.length; i++) {
    const pair = pairs[i].split('=');
    query[decodeURIComponent(pair[0])] = decodeURIComponent(pair[1] || '');
  }
  return query;
}

export abstract class RoutingInterceptor {

  protected constructor(
    private router: Router
  ) {
  }

  init() {
    // this code should be called from a top-level initialization, such as OnInit of AppComponent
    this.router.events
      .pipe(
        filter(event => event instanceof NavigationStart),
        pairwise()
      )
      .subscribe(this.routeChanged());
  }

  // This is the method you should implement to override routing
  protected abstract onRouteChanged(sourceUrl: string, targetUrl: string): string;

  private routeChanged(): (eventPair: [NavigationStart, NavigationStart]) => void {
    return ([previousEvent, currentEvent]: [NavigationStart, NavigationStart]) => {
      const sourceUrl = previousEvent.url;
      const targetUrl = currentEvent.url;

      const modifiedTargetUrl = this.onRouteChanged(sourceUrl, targetUrl);

      if (!modifiedTargetUrl || modifiedTargetUrl === targetUrl) {
        return;
      }

      if (modifiedTargetUrl.indexOf('?') !== -1) {
        const split = modifiedTargetUrl.split(('?'));
        const query = parseQuery(split[1]);
        this.router.navigate([split[0]], {queryParams: query});
      } else {
        this.router.navigate([modifiedTargetUrl]);
      }
    };
  }
}