Angular 6 – getting previous url from angular router

Below is a service that can be used to get the previous url from angular router where it is navigated via router or browser’s back button

// Service
import { Injectable } from '@angular/core';
import { Router, RouterEvent, NavigationEnd } from '@angular/router';

 /** A router wrapper, adding extra functions. */
@Injectable()
export class RouterExtService {

  private previousUrl: string = undefined;
  private currentUrl: string = undefined;

  constructor(private router: Router) {
    this.currentUrl = this.router.url;
    router.events.subscribe(event => {
      if (event instanceof NavigationEnd) {
        this.previousUrl = this.currentUrl;
        this.currentUrl = event.url;
      }
    });
  }

  public getPreviousUrl() {
    return this.previousUrl;
  }
}

Usage in component

 constructor(
    private routerService: RouterExtService
    ) {}

// referrer can be get from the service
const referrer = this.routerService.getPreviousUrl();