this issue is not reproducible - the kata is currently solvable. this is likely due to changes in the Node.JS environment / code runner setup for JS on Codewars (perhaps because Babel is no longer used - though I cannot replicate the issue even with the old Node v8.1.3/Babel version. But it would still be solvable even without that specific feature.

this issue is not reproducible.

var helloWorld = function() {}

works fine for this kata

The sample tests use assertSimilar while the submission tests use assertDeepEquals. These assertions have slightly differing semantics: extending Array, I pass the full tests but I fail the getSplit sample test:

Expected: 
'{ pass: [ \'a\', \'b\', \'c\' ], fail: [ 1, 2, 3 ] }'
, instead got: 
'{ pass: MagicArray [ \'a\', \'b\', \'c\' ],\n  fail: MagicArray [ 1, 2, 3 ] }'

suggested tag: restricted

and yet I like my solution better

JS: Node v14 should be used along with its appropiate assertion tools (Mocha + Chai).
Refer to this and this

Very creative, I wish I could think similar solutions involving many methods

eq: function(n) - Return an array with all methods, only containing the eq item...

This description makes zero sense; the expected behavior is extracting the n'th element of an array.

Your task is to make an object and add to it the following methods...

This is not enforced.

alr added some time ago

Maybe I'm looking at this wrong but is this finding the index of a letter in a string in an array in the c.indexOf portion?

Very funny kata.. thanks:)

using filter you loop 2 times on the arr. using reduce is the best practice !

If base is not supplied, it will create a new class entirely from Proto.

This doesn't seem to be tested at all.