INR currency format

Question

I need to show currency format like these, how can we show.

₹1
₹10
₹100
₹1,000
₹10,000
₹1,00,000
......

Answer 1

1. Get the digits before last three.
2. Replace the rest of the digits with prefix.replace(/\B(?=(?:\d{2})+(?!\d))/g, ",")
3. Combine the above section with this modified prefix

Complete explanation on why this regex places commas at the right place is is mentioned here.