The check is for blank spaces because

 will save all your white-space. aas well as the css-style { white-space: pre; }
Essentially: it's implementation use case.

Thank you for making this Kata.
I really enjoyed it.

I completed this Kata in JavaScript, but I'm curious about why white spaces (' ') are accpeted between words, but non-breaking spaces ('\xa0') are not accepted.

As far as I know, non breaking spaces do not collapse when rendered in HTML, while normal spaces might be collapsed.

Thanks.

Good! I'm glad for you:-)

Thanks again :)
My first algorithm was too slow, by selecting Node v0.10 in the dropdown menu and submitting the solution I saw it time out after 130 tests.
The error message I reported in my first post appeared with the default settings, Node v6 selected (and the message was quite confusing, because it seemed something server side).

My second algorithm had a "isPrime" function, but was slow because I was creating an array with all primes up to "n".

After some more attempts I managed to get it right.

Nice challenge :)

i tried running it and it still shows me the same error

Sieve is a good way but you don't need it here. I think you only need a isPrime function.

For the first error maybe you could try again and if that doesn't work report it as a bug: https://github.com/Codewars/codewars.com/issues.

Python and Ruby translations submitted, if you want to approve them :)

[Extra kudos for the effort on the test cases, quite detailed and well-written, but I will tell you more on them possibly later]