There is no need to pass the entire event (unless you need other aspects of the event than you have stated). In fact, it is not recommended. You can pass the element reference with just a little modification.
import {Component} from 'angular2/core';
@Component({
selector: 'my-app',
template: `
`
})
export class AppComponent {
buttonValue: string;
toggle(button) {
this.buttonValue = button.id;
}
}
StackBlitz demo
Technically, you don't need to find the button that was clicked, because you have passed the actual element.
Angular guidance