Tablesorter doesn't work with node

I can't manage to get the tablesorter to be working with node and webpack.

It is successully installed.

Example of my code is:

require('tablesorter')

$(function() {
  
  // some procedures
  $('#testtable').tablesorter()

})

The error it throws is: "Uncaught TypeError: $(...).tablesorter is not a function"

I have to mention, that it works just all fine if the tablesorter is included as a script via html in head.