How to use index column with data source

I am trying to use an index column that automatically shows row counter based on sort.

I am using this example: https://datatables.net/examples/api/counter_columns.html

But I can't figure out how to get it to work when using "columns" as well.

This is what my code looks like: https://hastebin.com/egegisuraq.js

I believe the issue is related to the fact I specified my columns with "columns" but I don't know how to specify a placeholder for this rendered column that represents the row ID based on current sort. I tried using "null" but that did not work.