<li *ngFor="let item of items; index as i; trackBy: trackByFn">...</li>
//for <div *ngFor='let [data] of [dataArray]; let i=index;'> <h2> {{i}} {{data.title}} </h2> <img src='{{data.image}}' /> </div> //the data contained in an array will be displayed element by element //similar to the function .map() in React