angular - Angular2: How to find out what was previous page url when using angular2 routing -

i developing angular2 app , use router. in page /myapp/signup. after signup navigate use /myapp/login. /myapp/login can navigated home page /myapp. now, when user users /myapp/login go back. can done using location.back(). dont want go when user coming /myapp/signup. should check if user coming /myapp/signup , if so, want direct somewhere else. how can know previous url direct user specific state based on ?

the pairwise operator allows current previous value

update  

import 'rxjs/add/operator/pairwise'; import {router} '@angular/router;  export class appcomponent {     constructor(private router: router) {         this.router.events         .filter(e => e instanceof navigationend)         .pairwise().subscribe((e) => {             console.log(e);         });     } } 

see how detect route change in angular 2?

original (super old)

inject router , subscribe events , store them later reference

constructor(private _router: router) {   this._router.subscribe(route => {     this.nextroute ...     this.prevroute ...   });