ngfor

<ul>
    <li *ngFor="let item of items; let i = index" [attr.data-index]="i">
        {{item}}
    </li>
</ul>

//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

      <li *ngFor="let item of items; index as i; trackBy: trackByFn">...</li>
    

let array = [1,2,3];
for (let i = 0; i < array.length; i++) {
  console.log(array[i]);
}