ngFor

TS

export class AppComponent {
    courses = [
        { id: 1, name: 'Course 1'},
        { id: 2, name: 'Course 2'},
        { id: 3, name: 'Course 3'},
    ];
}

html

<ul>
    <li *ngFor="let course of courses; index as i">
        {{i}} - {{course.name}}
    </li>
</ul>

ngForOf

<ul>
    <li *ngFor="let course of courses; even as isEven">
        {{course.name}} <span *ngIf="isEven">EVEN</span>
    </li>
</ul>