How to set focus on a dynamically added text area (angular material)

<button (click)="addTextArea()">Add Comment</button>

<div formArrayName="comments">
  <div *ngFor="let comment of commentsArray.controls; let i=index>
    <textarea>{{comment.value..}}</textarea>
  </div>
</div>

addTextArea() {
 const fc1 = this.fb.control('', [Validators.required]);
 const fc2 = this.fb.control('', [Validators.required]);

 this.commentsArray.insert(0,
   this.fb.group({
      code: fc1,
      value:fc2
   }


}

What I want to do is set focus on the newly added textarea. How would I do that. Thanks