JAVASCRIPT

angular material dropdown menu

<mat-menu #animals="matMenu">
  <button mat-menu-item [matMenuTriggerFor]="vertebrates">Vertebrates</button>
  <button mat-menu-item [matMenuTriggerFor]="invertebrates">Invertebrates</button>
</mat-menu>

<mat-menu #vertebrates="matMenu">
  <button mat-menu-item [matMenuTriggerFor]="fish">Fishes</button>
  <button mat-menu-item [matMenuTriggerFor]="amphibians">Amphibians</button>
  <button mat-menu-item [matMenuTriggerFor]="reptiles">Reptiles</button>
  <button mat-menu-item>Birds</button>
  <button mat-menu-item>Mammals</button>
</mat-menu>