output1.component.ts

import { Component, EventEmitter, Output } from '@angular/core';
 
@Component({
    selector: 'app-child',
    template: `<button class='btn btn-primary' (click)="food()">Click me</button> `
})
export class AppChildComponent {
 
    @Output() foo = new EventEmitter();
    index = 0;
 
    food() { 
        this.index = this.index + 1;
        this.foo.emit(this.index);
    }
}