you are using global variables, don't do that. they keep their values between function calls

OP solved it, closing

Reading the description should make the condition for m being undefined very obvious.

Is there a way to know if m exists or not(a Boolean)?

There are certain conditions that imply that there is no m. If you look carefully at the sample tests, those conditions might become clear. I can't really say more without adding a spoiler.

tbh, upon appropriate reflection, I agree that full disclosure with explicit specs is generally the best approach

Indeed. I think that's very very justified for a number with thousands of digits.

NOTE: m can be very very LARGE

so, that's TWO (2) verys

Added: "Where necessary, the way of handling big integers appropriate to the language should be used."

Did you think that 4300 digits would fit into the Number type? Of course there's no way that is possible. The mention of 4300 digits is enough to tell you that.

?? read the description

Added

That is to give the ASCII-ART the trianglular space / representation. Surely, this is not the only ASCII-ART kata that expects leading spaces !

Fixed.

Both issues fixed in this fork.
I'm using assert.sameOrderedMembers, because the chai assert.deepEqual discriminates between +0 and -0 for some reason. sameOrderedMembers instead uses === for comparison.