That´s strange...
Ok, copy and pased the code from here in the forum and it worked?!

Thanks for the pointer regarding my x var!

I was able to pass the tests from copy pasting your code so I can't speak to what the difference is, but I noticed you have a spurious global 'x' when you pass index + 1 to arrString.includes(). It works because the "x = index + 1" returns the new value of x, so its equiveleant to just "index + 1"