OP solved it, closing

loop through the array of numbers ([1,2,4,8,16]), check if n (2) is within it using your language's builtin function (if any) or another loop if not any!

Sorry, I don't know JavaScript. I think you would find help sooner if you posted at least part of your code here.

a or b might be [] (all languages except R, Shell). a or b might be nil or null or None or nothing (except in Haskell, Elixir, C++, Rust, R, Shell, PureScript).

You have to test if it's an array before trying to sort it.

You need to make sure what you're trying to sort is an array first.

Anyone who has completed the kata.

As soon as someone translates it ;-)

Read this.

You wrote Plays instead of plays there.

Don't create another post for the same problem, read my answer below in the post below.

Spot the difference:

Expected:    'Ringo plays banjo'
instead got: 'Ringo Plays banjo'

Your code has a typo. The comparison isn't case insensitive.