Tests added.

name: either a camelCase identifier consisting of letters only, or a single underscore '_' for an undefined value. names are not limited to a single character.

Not every name that is valid in JS is valid in this kata, as specified in the description. So none of those names you want is valid. Excluding that.

=== is not defined; that'll have to be ==.

Also, note that 5 + ! 0 + 3 can have any value greater than or equal to 9, because any positive number is truthy. As soon as ! 0 appears in any expression, the only unambiguous continuation is as a Boolean. Nothing should keep you from returning 2 for ! 0 ! ( Or 1, or 1 000. )

I had the same misunderstanding and asked myself how I can achieve the logic with only 5 bytes left after input and output...

😅Ahaha, sorry. Took me 12 myself

I probably meant "if the argument is not passed to the function on invocation, the value of that argument defaults to a value of 5". Though I can see how the wording might be a bit confusing.

for sure yeah...

Expecting a solution to a potential purple kata only hours after posting, is a little optimistic ;)

?? why are you posting this, exactly?

It looks like the author decided not to do other tests :]

spoiler flag! x/