bootstrap 4 in Angular 2 dropdown not working

Question

I have followed the following to install bootstrap 4 into my Angular 2 project: Accepted Answer, following the first 1,2,3 and 4 steps

However when I add the following <

Answer 1

Like Andrien's said, you can simplify the code like this.

constructor(private _el: ElementRef) { }

@HostBinding('class.show') isOpen = false;

@HostListener('click') toogleOpen() {
    this.isOpen = !this.isOpen;
    this._el.nativeElement.querySelector('.dropdown-menu').classList.toggle('show')
}