gistfile1.txt

<a *ngIf="windowScrolled" (click)="scrollUp()">
    <span class="scroll-top">
      <
    </span>
  </a>
  
  import { DOCUMENT } from '@angular/common';
  windowScrolled: boolean;
  lamp = faLightbulb;

  constructor(
    private localStorageService: LocalStorageService,
    @Inject(DOCUMENT) private document: Document) {
    
  @HostListener('window:scroll', [])
  onWindowScroll() {
    this.windowScrolled = window.pageYOffset > 250 ? true : false;
  }

  scrollUp() {
    document.querySelector('nav').scrollIntoView({ behavior: 'smooth', block: 'start' });
  }