title: Angular get ElementRef of of the routerLinkActive
body: <p>As in the title I need to get the ElementRef of the routerLinkActive in order to understand where I need to place an "ink Bar" (e.g. Material Design Tab) in the right position.</p>
  
  <p>here I there is my sideNav menu</p>
  
  <pre><code>  &lt;mat-sidenav fxLayout='column' 
     fxLayoutAlign='start center'#sidenav 
     mode="over" [(opened)]="opened" position="end" 
     class="nav-sidenav"&gt;
  
          &lt;!-- Here the Navigation --&gt;
          &lt;div  class="nav-sidenav-container" fxFlex='1 1 100%'&gt;
  
            &lt;div class="ink-bar"&gt;&lt;/div&gt; &lt;!-- I NEED TO MOVE THIS --&gt;
            &lt;ul class="nav"&gt;
  
              &lt;li *ngFor="let menuItem of menuItems" 
               routerLinkActive="active" class="{{menuItem.class}}"&gt;
                &lt;a [routerLink]="[menuItem.path]"&gt;
                  &lt;i class="nav-icon-container"&gt;
                    &lt;mat-icon&gt;{{menuItem.icon}}&lt;/mat-icon&gt;
                  &lt;/i&gt;
                  &lt;p&gt;{{menuItem.title}}&lt;/p&gt;
                &lt;/a&gt;
              &lt;/li&gt;
  
            &lt;/ul&gt;
          &lt;/div&gt;
        &lt;/mat-sidenav&gt;
  </code></pre>
  
  <p>the first "li" element is at 180px the offset between the elements is 60px. But i need to know which is the active element at the beginning (e.g. if user paste the URL in the browser), there is a way to get the ElementRef of the activeLink</p>