a list of non-negative integers and strings

The problem statement mentions two kinds of values, so if it's not one, then it's the other. There's no second thing you can test.

The spec doesn't say that there should be any such check, it even says that there won't be any NaN (why would there be?)

This solution has no NaN checks.

Insightful!

The question says 'a function that takes a list of non-negative integers'.
so there wouldn't be any array with negative numbers.
plus that I don't understand why u said in your exmaple it should return only 2 and 3. what about 3.5?

Great bro!

How it is beneficial to add an extra function inside when a simple call back will do ?

it clear and best practice too

I wonder why this code becomes best practices and clever!