export class MarvelHerosComponent implements OnInit {

  hero = ["IronMan","Hulk","Thor"]


    ChangeHero() {
        this.hero[1] = "Black Panther"
    }

}

<p>Hero 1 is {{hero[0]}}</p>
<p>Hero 2 is {{hero[1]}}</p>
<p>Hero 3 is {{hero[2]}}</p>

<button class="btn btn-success" (click)="ChangeHero()">Change Hero</button>