angular use index for array in the markup. code example

Example 1: how to get index for ngfor

*ngFor="let item of items; index as i;" 
// OR
*ngFor="let item of items; let i = index;"
// i will be the index, starting from 0 
// and you can show it in the string interpolation with {{ i }}

Example 2: ngfor index

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