SEO-SPA: DI Service Usage

usage.ts

//In app.browser.module.ts providers:

{
  provide: ElementFocusService,
  useClass: ElementFocusBrowserService
},

//In app.server.module.ts providers:

{
  provide: ElementFocusService,
  useClass: ElementFocusServerService
},

//Component usage:

import { Component, OnInit, ViewChild, ElementRef } from '@angular/core';
import { ElementFocusService } from '../../services/element-focus.service';

@Component({
  selector: 'app-look-at-me',
  template: `
    <p #myElement>I'm in focus now!</p>
  `,
  styleUrls: ['./look-at-me.component.scss']
})
export class LookAtMeComponent implements OnInit {
  @ViewChild('myElement') myElementRef: ElementRef;

  constructor(private focusElement: ElementFocusService) { }

  ngOnInit() {
    this.focusElement.focusElement(this.myElementRef);
  }
}