Awesome!

JS test is working fine at this point of time.

Clever, but it can do in one line.

Here you do all of the work and then throw it out if the input wasn't the right format. Granted this is a toy problem.. but this pattern is not best practice.

It should now work, let me know if not :)

I got the same. The last one in Example test cases is invalid, assuming that Kata Test Cases are valid.

Added.

Please, fix a small typo in description: not "and array" but "an array"

When I submit my solution I've got a strange otput:

TypeError: object is not a function
  at justify
  at .:136:11
  at Array.forEach
  at .:134:11
  at .:154:3
  
      
74 Passed
0 Failed
1 Errors

I can't understand why I have error with Array.forEach because my code if convert it to JavaScript doesn't include any Array.forEach. Can anybody help me?

It's strange but tests work differently when I click 'Run test' and 'Submit'.
I had my tests failed with incorrect argument when I use raise unless ... but same tests had passed when I click 'Submit'!