How do I detect user navigating back in Angular2?

Question

I have a component and I need to detect if user pressed back button in his browser to navigate back.

Currently I'm subscribing router events.

constructor(private router: Router, private activatedRoute: ActivatedRoute) {

    this.routerSubscription = router.events
        .subscribe(event => {

            // if (event.navigatesBack()) ...

        });

}

I know that I can use window.onpopstate but it feels like a hack when using Angular2.

Answer 1

It's possible to use PlatformLocation which has onPopState listener.

import { PlatformLocation } from '@angular/common'

(...)

constructor(location: PlatformLocation) {

    location.onPopState(() => {

        console.log('pressed back!');

    });

}

(...)

Answer 2

IMO better method of listenting for popstate events is to subscribe to location service

import {Location} from "@angular/common";

constructor(private location: Location) { }

ngOnInit() {
    this.location.subscribe(x => console.log(x));
}

It doesn't use PlatformLocation directly (as documentation suggest) and you can unsubscribe any time you want.

Answer 3

import { HostListener } from '@angular/core';

and then listen for popstate on the window object:

  @HostListener('window:popstate', ['$event'])
  onPopState(event) {
    console.log('Back button pressed');
  }

This code works for me on latest Angular 2.

Answer 4

As thorin87 answer dont use PlatformLocation. We need subscribe an unsubscribe.

import {Subscription} from 'rxjs/Subscription';    

ngOnInit() {
  this.subscription = <Subscription>this
    .location
    .subscribe(() => x => console.log(x));
}

ngOnDestroy() {
  this.subscription.unsubscribe();
}