browser forward and backward button in angular event

Question

I am new to angular 4 using typescript, how can we differentiate forward and backward button in the browser.

 

this.subscription = <Subscription>this.lc.subscribe((x: PopStateEvent) => { console.log("Localtion Back", x); // // Handler });

how to come out of the application stack:usecase assume user started with google.com then user type abc.com . In abc.com, user will navigate a>b>c>d>e then from e page navigate to b and if the user press browserback  button first time it should navigate to a thn second time back it should come back to google.com