Problem is the way it's written. It's fitted into one liner as a some kind of flex without care of readability. It would be better to split it into at least two lines. It's not a JS code that you need to save on spaces.

There should be "obfuscated" button for solutions like this.

It's not working if b=0 for any operator. Looks like test cases are badly written if this solution passed.

From kata details: "The size will always be positive and will only use whole numbers."
So, you don't care about 0.

Terrible solution. This is not how you should use exceptions...

n + 2 * n is still O(n)...

How this terrible solution can be Best Practice? Sometimes I don't understand how people throw votes here...