I have the same problem, any clue?

No need to loop through the whole room-list, even using filter you can do what you wanted i.e.

function roomMates( r, f ){
return r.slice((f-1)6,f6).filter(function(x){return x;})
}

+1

I'm stuck on the pipeline tests(submit), the first 4 test pass, but the 5th fails. It looks like the test has a function called _fifth and the seed is an array of numbers 1-9, my pipeline function returns 5, but test fails stating that it's looking for -5.

I like this as the best practice, because it only has to filter 6 items. The other solutions that don't use .slice have to itterate over the entire array.