Indicating that a link on the page is actually the current page we're looking at is a common UI pattern in web apps. Normally you would have to manually check whether the current URL matches the URL in the link, but many modern web frameworks provide you some sort of helper functionality for this.
Doing this with Angular 2's router is a total breeze — on any link you can just add the directive
routerLinkActive and pass along the name of whatever CSS class(es) you want to add when the current URL matches the URL in the link:
<a [routerLink]="['profile']" routerLinkActive="your-css-class">Eric's Profile</a>
The nice thing about
routerLinkActive is that it has complete knowledge of your app's routing structure, so you can configure it to behave in various ways depending on your specific requirements. You can learn about all of it's capabilities from the Angular docs.