A very efficent but sloppily formatted solution. Kind of funny to use /10 as the base check instead of just <10 which would be more efficient. A variant of this should be the best practice.

Short and sweet!

Arrow functions are not IIFE. This is just their syntax. If they are one line expressions they don't need return. But if they contain several lines of code, then they need return statement and curly braces around code block.

Does this work without the return statement because arrow functions are 'immediately invoked functions?'

this one excels

Thank you.

This is a very good solution: the highest performance (according to test results) and short code

Good one.

Apparently C# literally has any method you can think of

First time I do a oneliner and OBV someone does it shorter :D

don't even need semicolon