What is currently the best and most transparent way to debug JavaScript functions on a built site?

Question

JavaScript

What is currently the best and most transparent way to debug JavaScript functions on a built site? I just got tired of writing console.log and alert . With this method, it is not immediately possible to understand what exactly went wrong, that is, why the function does not work out. I would like to have a deeper approach to debugging.
I use Sublime Text 3. I use
Gulp and compile html and less files
. I saw somewhere that it is possible from under the editor, inside the editor itself, for example, to see what exactly is in the variable, or from the editor to mark from which part and which part the debug will go through, while not affecting other parts. In general, what plugins can you tell me to work in Sublime Text 3 and output via gulp in Mozilla Firefox.

Answer 1

debugger in FF

Answer 2

debugger