app.component.ts

@Component({
    selector: 'app', 
    template: `<ul>
                    <li *ngFor="let item of items; trackBy: trackById">{{item.name}}</li>
               </ul>`
})
class AppComponent {
    Items = [
        {
            id: 1,
            name: 'item 1'
        }, {
            id: 2,
            name: 'item 2'
        },
        ...
    ];
    trackById(index, item) {
        return item.id;
    }
}