@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;
}
}