Angular2 Detect if element in template view has class

Question

Add a template variable to be able to query the element.

<div #patientDDL class="overlay-dropdown dropdown" id="patientDDL">

Query the element

@ViewChild('patientDDL') patientDDL:ElementRef;

Implement ngDoCheck() to run the check whether the class was added when change detection runs:

ngDoCheck() {
  if(patientDDL.nativeElement.classList.contains('open')) {
    this.doSomething();
  }
}

or on some specific event

@HostListener('click', ['$event'])
clickHandler(event) {
  if(patientDDL.nativeElement.classList.contains('open')) {
    this.doSomething();
  }
}