Check out example codes for "how to get index for ngfor". It will help you in understanding the concepts better.

Code Example 1

*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 }}

Learn ReactJs, React Native from akashmittal.com