Definitely. As long as you know where to start.

Is this 6kuy kata?

good solution, but it doesn't check for alpha, now we can pass not only letters!

For example this call in this solution findMissingLetter(['<','>']) return us '=' which is not a letter actually

You don't need to reassign the array variable like this 'array = array.sort', because sort() is already mutating the array, also be afraid that it will mutate the initial array from the argument, hence better to do something like this 'const innerArray = [...array] and work with it.

True, replacing nums with [...nums] would fix it if that is needed

Be careful. This solution will change the initial array.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort
"Note that the array is sorted in place, and no copy is made."

3 years later - I got it, thank you for awesome answer )

formula from elementary school math textbook

Oh, I am not alone in using subtraction instead of division :))

From their brain.

How did u find solution like that?