That's true. However this solution is really old, probably written before var became depricated.

It is better not to use var and replace it with let or const, but in this case let. It is better not to use var at all

What about number which is a string? ( ͡° ͜ʖ ͡°)

Every language that is not C or Brainfuck has this function.

HAHA kinda feels unfair using python, purpose of this is to be able to develop the built in function or something like it hence improving our problem solving.

Please use appropriate formatting when posting code (code blocks)!

You would have higher chance of getting help if you asked concrete questions and showed more initiative, and not just "fix my code for me".

Debug your solution and try to understand what is going wrong yourself. Debugging is an essential skill in programming and by asking other people to do it you're doing a disservice to yourself. Maybe this can help: https://docs.codewars.com/training/troubleshooting

Please use the spoiler flag when posting potential spoilers and use appropriate formatting when posting code. See: https://docs.codewars.com/training/troubleshooting#post-discourse

[...] in my opinion my code is correct and definitely works on vscode

Your code doesn't do what the kata asks at all, so I'm not sure what you mean by "correct".

You need to be able to handle any function, not just the 4 you hardcoded. The functions are also passed in as functions, not as strings.