[conistonwater]

I think you misunderstood the Euclidean algorithm. The basic iteration is of the form

    gcd(a, b) = gcd(b, a mod b),

and there is no need to compute mod with anything other than %.

[feliperibeiro]

You're right. This is the subtraction-based implementation, the division-based is the original and better one :)

https://github.com/felipernb/algorithms.js/commit/e5a04f9ad0...