how to add class only in inner pages not homepage

app.component.ts

export class AppComponent implements OnInit {
  previousUrl: any;
  constructor(private render: Renderer2, private router: Router) {
    this.router.events.subscribe(
      (event) => {
        if (event instanceof NavigationStart) {
          //for current page name
          let currentUrlSlug = event.url.slice(1);
          let currentUrlSlug2 = 'fixed-inner';
          if (this.previousUrl) {
            console.log('hit');
            this.render.removeClass(document.body, currentUrlSlug2);
          }
          if (currentUrlSlug) {
            this.render.addClass(document.body, currentUrlSlug2);
          }
          this.previousUrl = currentUrlSlug;
        }
      }
    )
  }
}

Now this fixed-inner class always show only on inner pages