How do I detect user navigating back in Angular2?

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.

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EDIT Please don't do this.

The official docs say "This class should not be used directly by an application developer. Instead, use Location." Ref: https://angular.io/api/common/PlatformLocation

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

import { PlatformLocation } from '@angular/common'

(...)

constructor(location: PlatformLocation) {

    location.onPopState(() => {

        console.log('pressed back!');

    });

}

(...)