Angular2: How to find out what was previous page url when using angular2 routing [duplicate]

Question

I am developing an angular2 app and I use router. I am in a page /myapp/signup. after signup I navigate the use to /myapp/login. /myapp/login can also be navigated from my home page which is /myapp. So now, when the user users /myapp/login I go back. This can be done by using location.back(). But I dont want to go back when the user is coming from /myapp/signup. So I should check if the user is coming from /myapp/signup and if so, I want to direct it to somewhere else. How can I know the previous url so that I direct the user to a specific state based on that ?

Answer 1

The pairwise operator allows to get the current together with the previous value

update  

import 'rxjs/add/operator/pairwise';
import 'rxjs/add/operator/filter';
import { Router, NavigationEnd } from '@angular/router';

export class AppComponent {
    constructor(private router: Router) {
        this.router.events
        .filter(e => e instanceof NavigationEnd)
        .pairwise().subscribe((e) => {
            console.log(e);
        });
    }
}

See also How to detect a route change in Angular?

original (super old)

Inject Router and subscribe to events and store them for later reference

constructor(private _router: Router) {
  this._router.subscribe(route => {
    this.nextRoute ...
    this.prevRoute ...
  });