Convert jquery number counter to typescript

Without seeing your code, I am going to have to make some assumptions.

The first is that you haven't figured out what the purpose of the $ is at the start. That's an alias for JQuery itself so this part $(`.counter-count`) is effectively an alias for document.getElementsByClassName(`counter-count`);. Now, that returns an array so you can use something like forEach to iterate over it. If you use the fat arrow function implementation, you will get an explicitly captured this so you can discount $(this). This part would look a little bit like this

theClassArray.forEach(element => {
  // element takes the place of $(this)
});

As I don't know what else is wrong with your code, I'll leave it up to you - but you should have enough hints here.