Thanks! Big relief to finally be able to finish this and look at some other ways of doing it.

I added console.log('input = ', arr) at the beginning of your function and console.log('output = ', result) at the end, here is what I see:

input =  [ '', '', '', 'a', '', '' ]
output =  undefined

your function fails that tests case because your result variable is never assigned a value: the 3 consecutive ifs are not entered, then masterKey === [], so the loop is not entered either, so result remains undefined.

Hi, I would really appreciate some help with this as I have been working on it for days but can't pass it.
When I click Test, it passes, but when I Attempt it, it passes everything except 'should handle empty or spaces string'
with the message:
'Non-empty string in empty strings: expected undefined to equal 'a''
However when I test my function the log (including in the same screen as above) says it is returning a
Is there something obvious I'm missing?
I set up an if loop to test if there are any spaces in the array, which returns the array as a joined string with the spaces deleted if so. If not, it goes into the else loop which tests for the unique string.