Observable.fromEvent in angular5

hola.component.ts

import {AfterViewInit, Component, ElementRef, OnInit, ViewChild} from '@angular/core';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/observable/fromEvent';

@Component({
  selector: 'app-hola',
  template: `
    <p>
      hola works!
      <button #hola>Hola!</button>
    </p>
  `,
  styleUrls: ['./hola.component.css']
})
export class HolaComponent implements AfterViewInit {

  @ViewChild('hola') button: ElementRef;

  ngAfterViewInit() {
    Observable.fromEvent(this.button.nativeElement, 'click')
      .subscribe(res => console.log(res));

  }

}